Genetically engineered hematopoietic stem cells and uses thereof

ABSTRACT

Genetically engineered hematopoietic cells such as hematopoietic stem cells having one or more genetically edited genes of lineage-specific cell-surface proteins and therapeutic uses thereof, either alone or in combination with immune therapy that targets the lineage-specific cell-surface proteins.

This application claims priority to U.S. Ser. No. 62/723,993 filed Aug. 28, 2018, U.S. Ser. No. 62/728,061 filed Sep. 6, 2018, U.S. Ser. No. 62/789,440 filed Jan. 7, 2019, and U.S. Ser. No. 62/809,202 filed Feb. 22, 2019, the entire contents of each of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

A major challenge in designing targeted therapies is the successful identification of proteins that are uniquely expressed on cells that would be therapeutically relevant to eliminate (e.g., abnormal, malignant, or other target cells) but not present on cells that one does not wish to eliminate (e.g., normal, healthy, or other non-target cells). For example, many cancer therapeutics struggle to effectively target cancer cells while leaving normal cells unharmed.

An alternative strategy that has emerged involves targeting an entire cell lineage, which includes targeting normal cells, cancer cells, and pre-cancerous cells. For example, CD19-targeted chimeric antigen receptor T cells (CAR T cells) and anti-CD20 monoclonal antibodies (e.g. Rituximab) each target B cell lineage proteins (CD19 and CD20, respectively). While potentially effective in treating B cell malignancies, use of such therapies is limited as elimination of B cells is detrimental. Similarly, targeting lineage-specific proteins of other cell populations, for example, myeloid lineage cells (e.g., cancers arising from myeloid blasts, monocytes, megakaryocytes, etc) is not feasible, as these cell populations are necessary for survival.

Thus, there remains an unmet need to effectively target cells of interest, e.g., cancer cells, without targeting or harming normal cell populations.

SUMMARY OF THE INVENTION

Provided herein are compositions, e.g., engineered cells, and methods that provide the ability to target one or more cells or cell populations of interest while allowing non-targeted cell populations to escape such targeting. For example, provided herein are genetically engineered hematopoietic cells such as hematopoietic stem cells (HSCs) having genetically modified or edited genes of one or more lineage-specific cell-surface antigens. In some embodiments, the modified, e.g., edited genes are able to produce the lineage-specific cell surface proteins in modified form, which retain, at least partially, the biological activity of the lineage-specific cell-surface antigens in the HSCs or in descendant cells expressing such, but can escape targeting by cytotoxic agents that are specific to the wild-type lineage-specific cell-surface antigens. In some embodiments, the modified, e.g., edited, genes do not produce the lineage-specific cell surface protein(s) or produce a truncated version of the lineage-specific cell surface protein(s) that, while able to escape targeting by cytotoxic agents that are specific to the wild-type lineage-specific cell-surface antigen(s), may not retain biological activity of the lineage-specific cell-surface antigen(s) in the HSCs or in descendant cells expressing such.

Thus, provided herein are genetically engineered hematopoietic cells, such as hematopoietic stem cells (HSCs), having one or more modified lineage-specific cell-surface antigen. In some embodiments, the one or more modified lineage-specific cell surface proteins are modified such that one or more of the lineage-specific cell surface proteins retain at least partially its biological activity of the lineage-specific cell-surface antigens in the HSCs or in descendant cells expressing such, but can escape targeting by cytotoxic agents that are specific to the corresponding wild-type lineage-specific cell-surface antigen(s). In some embodiments, the one or more modified lineage-specific cell surface proteins are modified such that all of the modified lineage-specific cell surface proteins (e.g., one, two, three, four, etc.) retain at least partial biological activity. In some embodiments, the one or more modified lineage-specific cell surface proteins are modified such that at least one, but not all, of the modified lineage-specific cell surface protein(s) retain at least partial biological activity. In some embodiments, the one or more modified lineage-specific cell surface proteins are modified such that one or more of the lineage-specific cell surface proteins do not retain at least partial biological activity of the lineage-specific cell-surface antigens in the HSCs or in descendant cells expressing such, but can escape targeting by cytotoxic agents that are specific to the corresponding wild-type lineage-specific cell-surface antigen(s). In some embodiments, the one or more modified lineage-specific cell surface proteins are modified such that none of the modified lineage-specific cell surface protein(s) retain at least partial biological activity. Thus, the genetically engineered hematopoietic cells provided herein having one or more modified lineage-specific cell-surface antigens can escape targeting by cytotoxic agents that are specific to the corresponding wild-type lineage-specific cell-surface antigen(s) and may comprise modified lineage-specific cell-surface antigen(s) that retain at least partial biological activity and/or may comprise lineage-specific cell-surface antigen(s) that do not retain biological activity (e.g., the protein may be knocked out).

The genetically engineered hematopoietic cells provided herein having genetically modified or edited genes of one or more lineage-specific cell-surface antigens are useful in therapies, e.g., immunotherapies and other cytotoxic agents, that specifically target cells expressing a lineage-specific cell-surface antigen, by virtue of the fact that the genetically engineered hematopoietic cells produce one or more modified lineage-specific cell-surface antigen(s) that are able to escape such targeting while retaining their biological activity. Accordingly, with such engineered hematopoietic cell it is possible to target or direct immunotherapies or other cytotoxic agents against a lineage-specific cell-surface antigen that is required for survival of an organism. Also, with such engineered hematopoietic cell, it is possible to target or direct immunotherapies or other cytotoxic agents against a cell type required for survival of an organism expressing a targeted lineage-specific cell-surface antigen. In other embodiments, the genetically engineered hematopoietic cells provided herein having genetically modified or edited genes of one or more lineage-specific cell-surface antigens are useful in therapies, e.g., immunotherapies and other cytotoxic agents, that specifically target cells expressing a lineage-specific cell-surface antigen, by having the ability to escape such targeting even though that do not retain biological activity. With such engineered hematopoietic cell it is possible to target or direct immunotherapies or other cytotoxic agents against a lineage-specific cell-surface antigen that is not required for survival of an organism. Also, with such engineered hematopoietic cell, it is possible to target or direct immunotherapies or other cytotoxic agents against a cell type that is not required for survival of an organism expressing a targeted lineage-specific cell-surface antigen. In some embodiments, in which the genetically engineered hematopoietic cells have one or more modified lineage-specific cell-surface antigens, wherein one or more lineage-specific cell-surface antigens retain biological activity and wherein one or more lineage-specific cell-surface antigens do not retain biological activity, it is possible to target or direct immunotherapies or other cytotoxic agents against lineage-specific cell-surface antigen(s) that may or may not be required for survival of an organism. Also, with such engineered hematopoietic cell, it is possible to target or direct immunotherapies or other cytotoxic agents against a cell type that may or may not be required for survival of an organism expressing a targeted lineage-specific cell-surface antigen.

In some aspects, the genetically engineered hematopoietic cell is genetically modified or edited such that it produces one modified or mutated lineage-specific cell-surface antigen that retains biological activity, but escapes targeting by a cytotoxic agent specific to the wild-type lineage-specific cell-surface antigen. In some aspects, the genetically engineered hematopoietic cell is genetically modified or edited such that it produces two or more (e.g., 2, 3, 4, 5, etc) modified or mutated lineage-specific cell-surface antigens that escape targeting by a cytotoxic agent specific to (or that targets) the corresponding wild-type lineage-specific cell-surface antigens. In some embodiments of these latter aspects, at least one of the modified or mutated lineage-specific cell-surface proteins retains its biological activity. In some embodiments, two or more of the modified or mutated lineage-specific cell-surface antigens retain their respective biological activities. In some embodiments, all of the modified or mutated lineage-specific cell-surface antigens expressed in the genetically engineered hematopoietic cell retain (at least partially) their respective biological activities.

Accordingly, one aspect of the present disclosure features a genetically engineered hematopoietic cell, comprising: (i) a first gene encoding a first lineage-specific cell-surface antigen, which gene has been modified or edited and (ii) a second gene encoding a second lineage-specific cell-surface antigen, which gene has been modified or edited. In some embodiments, the first gene has been modified or edited such that expression of the first lineage-specific cell-surface antigen is reduced or eliminated in the genetically engineered hematopoietic cell (e.g., as compared with expression of the corresponding endogenous or wild-type lineage-specific cell-surface antigen). In some embodiments, the first gene has been modified or edited such that the genetically engineered hematopoietic cell expresses a mutant or modified version of the first lineage-specific cell-surface antigen. In some embodiments, the mutant or modified version of the first lineage-specific cell-surface antigen escapes targeting by a cytotoxic agent that targets the corresponding wild-type lineage-specific cell-surface antigen. In some embodiments, the mutant or modified version of the first lineage-specific cell-surface antigen retains its biological activity. In some embodiments, the mutant or modified version of the first lineage-specific cell-surface antigen escapes targeting by a cytotoxic agent that targets the corresponding wild-type lineage-specific cell-surface antigen and retains its biological activity. In some embodiments, the second gene has been modified or edited such that expression of the second lineage-specific cell-surface antigen is reduced or eliminated in the genetically engineered hematopoietic cell (e.g., as compared with expression of the corresponding endogenous or wild-type lineage-specific cell-surface antigen). In some embodiments, the second gene has been modified or edited such that the genetically engineered hematopoietic cell expresses a mutant or modified version of the second lineage-specific cell-surface antigen. In some embodiments, the mutant or modified version of the second lineage-specific cell-surface antigen escapes targeting by a cytotoxic agent that targets the corresponding wild-type lineage-specific cell-surface antigen. In some embodiments, the mutant or modified version of the second lineage-specific cell-surface antigen retains its biological activity. In some embodiments, the mutant or modified version of the second lineage-specific cell-surface antigen escapes targeting by a cytotoxic agent that targets the corresponding wild-type lineage-specific cell-surface antigen and retains its biological activity. In some embodiments, the mutant or modified versions of the first and second lineage-specific cell-surface antigens retain their respective biological activities. In some embodiments, the mutant or modified version of the first lineage-specific cell-surface antigen retains its biological activity and the mutant or modified version of the second lineage-specific cell-surface antigen does not retain its biological activity. In some embodiments, neither the mutant or modified version of the first lineage-specific cell-surface antigen retains its biological activity nor the mutant or modified version of the second lineage-specific cell-surface antigen retains its biological activity.

Another aspect of the present disclosure features a genetically engineered hematopoietic cell, comprising: (i) a first gene encoding a first lineage-specific cell-surface antigen, which gene has been modified or edited; (ii) a second gene encoding a second lineage-specific cell-surface antigen, which gene has been modified or edited; and (iii) a third gene encoding a third lineage-specific cell-surface antigen, which gene has been modified or edited. In some embodiments, the genetically engineered hematopoietic cell further comprises (iv) a fourth gene encoding a fourth lineage-specific cell-surface antigen, which gene has been modified or edited. In some embodiments, the genetically engineered hematopoietic cell further comprises (v) a fifth gene encoding a fifth lineage-specific cell-surface antigen, which gene has been modified or edited.

In some embodiments, any one or more of the gene(s) encoding a lineage-specific cell-surface antigen has been modified or edited such that expression of the respective lineage-specific cell-surface antigen(s) is reduced or eliminated in the genetically engineered hematopoietic cell (e.g., as compared with expression of the corresponding endogenous or wild-type lineage-specific cell-surface antigen). In some embodiments, any one or more of the gene(s) encoding a lineage-specific cell-surface antigen has been modified or edited such that the genetically engineered hematopoietic cell expresses a mutant or modified version of the respective lineage-specific cell-surface antigen(s).

In some embodiments, any one or more of the mutant lineage-specific cell-surface antigen(s) escapes targeting by a cytotoxic agent that targets the corresponding wild-type lineage-specific cell-surface antigen. In some embodiments, any one or more of the mutant lineage-specific cell-surface antigen(s) retains its biological activity. In some embodiments, any one or more of the mutant lineage-specific cell-surface antigen(s) escapes targeting by a cytotoxic agent that targets the corresponding wild-type lineage-specific cell-surface antigen and retains its biological activity.

Another aspect of the present disclosure features a population of genetically engineered hematopoietic cells, wherein the genetically engineered hematopoietic cells in the population comprise: (i) a first gene encoding a first lineage-specific cell-surface antigen, which gene has been modified or edited and (ii) a second gene encoding a second lineage-specific cell-surface antigen, which gene has been modified or edited. In some embodiments, the first gene has been modified or edited such that expression of the first lineage-specific cell-surface antigen is reduced or eliminated in the genetically engineered hematopoietic cell (e.g., as compared with expression of the corresponding endogenous or wild-type lineage-specific cell-surface antigen). In some embodiments, the first gene has been modified or edited such that the genetically engineered hematopoietic cell expresses a mutant or modified version of the first lineage-specific cell-surface antigen. In some embodiments, the mutant or modified version of the first lineage-specific cell-surface antigen escapes targeting by a cytotoxic agent that targets the corresponding wild-type lineage-specific cell-surface antigen. In some embodiments, the mutant or modified version of the first lineage-specific cell-surface antigen retains its biological activity. In some embodiments, the mutant or modified version of the first lineage-specific cell-surface antigen escapes targeting by a cytotoxic agent that targets the corresponding wild-type lineage-specific cell-surface antigen and retains its biological activity. In some embodiments, the second gene has been modified or edited such that expression of the second lineage-specific cell-surface antigen is reduced or eliminated in the genetically engineered hematopoietic cell (e.g., as compared with expression of the corresponding endogenous or wild-type lineage-specific cell-surface antigen). In some embodiments, the second gene has been modified or edited such that the genetically engineered hematopoietic cell expresses a mutant or modified version of the second lineage-specific cell-surface antigen. In some embodiments, the mutant or modified version of the second lineage-specific cell-surface antigen escapes targeting by a cytotoxic agent that targets the corresponding wild-type lineage-specific cell-surface antigen. In some embodiments, the mutant or modified version of the second lineage-specific cell-surface antigen retains its biological activity. In some embodiments, the mutant or modified version of the second lineage-specific cell-surface antigen escapes targeting by a cytotoxic agent that targets the corresponding wild-type lineage-specific cell-surface antigen and retains its biological activity.

Another aspect of the present disclosure features a population of genetically engineered hematopoietic cells, wherein the genetically engineered hematopoietic cells of the population further comprise: (iii) a third gene encoding a third lineage-specific cell-surface antigen, which gene has been modified or edited. In some embodiments, the genetically engineered hematopoietic cells of the population further comprise: (iv) a fourth gene encoding a fourth lineage-specific cell-surface antigen, which gene has been modified or edited. In some embodiments, the genetically engineered hematopoietic cells of the population further comprise (v) a fifth gene encoding a fifth lineage-specific cell-surface antigen, which gene has been modified or edited. In some embodiments, any one or more of the gene(s) encoding a lineage-specific cell-surface antigen has been modified or edited such that expression of the respective lineage-specific cell-surface antigen(s) is reduced or eliminated in the genetically engineered hematopoietic cell (e.g., as compared with expression of the corresponding endogenous or wild-type lineage-specific cell-surface antigen). In some embodiments, any one or more of the gene(s) encoding a lineage-specific cell-surface antigen has been modified or edited such that the genetically engineered hematopoietic cell expresses a mutant or modified version of the respective lineage-specific cell-surface antigen(s). In some embodiments, any one or more of the mutant lineage-specific cell-surface antigen(s) escapes targeting by a cytotoxic agent that targets the corresponding wild-type lineage-specific cell-surface antigen. In some embodiments, any one or more of the mutant or modified version lineage-specific cell-surface antigen(s) retains its biological activity. In some embodiments, any one or more of the mutant lineage-specific cell-surface antigen(s) escapes targeting by a cytotoxic agent that targets the corresponding wild-type lineage-specific cell-surface antigen and retains its biological activity. One aspect of the present disclosure features a population of genetically engineered hematopoietic cells, comprising: (i) a first group of genetically engineered hematopoietic cells, which have genetic modification or editing in a first gene encoding a first lineage-specific cell-surface antigen, wherein the first group of genetically engineered hematopoietic cells (a) have reduced or eliminated expression of the first lineage-specific cell-surface antigen or (b) express a mutant of the first lineage-specific cell-surface antigen; and (ii) a second group of genetically engineered hematopoietic cells, which have genetic modification or editing in a second gene encoding a second lineage-specific cell-surface antigen, wherein the second group of genetically engineered hematopoietic cells (a) have reduced or eliminated expression of the second lineage-specific cell-surface antigen or (b) express a mutant of the second lineage-specific cell-surface antigen. In some embodiments, the first group of genetically engineered hematopoietic cells may overlap with the second group of genetically engineered hematopoietic cells, completely or partially.

In some embodiments, the present disclosure provides a genetically engineered hematopoietic cell, comprising: (i) a gene encoding a CD19, which gene has been modified or edited and (ii) a gene encoding a CD33, which gene has been modified or edited. In some embodiments, the CD19 gene has been modified or edited such that expression of the CD19 antigen is reduced or eliminated in the genetically engineered hematopoietic cell (e.g., as compared with expression of the corresponding endogenous or wild-type CD19 antigen). In some embodiments, the CD19 gene has been modified or edited such that the genetically engineered hematopoietic cell expresses a mutant or modified version of the CD19 antigen. In some embodiments, the mutant or modified version of the CD19 antigen escapes targeting by a cytotoxic agent that targets the corresponding wild-type CD19 antigen. In some embodiments, the mutant or modified version of the CD19 antigen retains its biological activity. In some embodiments, the mutant or modified version of the CD19 antigen escapes targeting by a cytotoxic agent that targets the corresponding wild-type CD19 antigen and retains its biological activity. In some embodiments, the CD33 gene has been modified or edited such that expression of the CD33 antigen is reduced or eliminated in the genetically engineered hematopoietic cell (e.g., as compared with expression of the corresponding endogenous or wild-type CD33 antigen). In some embodiments, the CD33 gene has been modified or edited such that the genetically engineered hematopoietic cell expresses a mutant or modified version of the CD33 antigen. In some embodiments, the mutant or modified version of the CD33 antigen escapes targeting by a cytotoxic agent that targets the corresponding wild-type CD33 antigen. In some embodiments, the mutant or modified version of the CD33 antigen retains its biological activity. In some embodiments, the mutant or modified version of the CD33 antigen escapes targeting by a cytotoxic agent that targets the corresponding wild-type CD33 antigen and retains its biological activity. In some embodiments of the genetically engineered hematopoietic cell comprising: (i) a modified or edited gene encoding a CD19 and (ii) a modified or edited gene encoding a CD33, the gene encoding CD19 has been modified or edited such that the entire exon 2 is deleted or a portion of exon 2 is deleted. In some embodiments of the genetically engineered hematopoietic cell comprising: (i) a modified or edited gene encoding a CD19 and (ii) a modified or edited gene encoding a CD33, the gene encoding CD33 has been modified or edited such that the entire exon 2 is deleted or a portion of exon 2 is deleted. In some embodiments of the genetically engineered hematopoietic cell comprising: (i) a modified or edited gene encoding a CD19 and (ii) a modified or edited gene encoding a CD33, the gene encoding CD19 has been modified or edited such that the gene is truncated, has inserted and/or deleted sequences (e.g., resulting in scrambled, frameshift, or nonsense sequence), or the entire gene is deleted (e.g., effectively a knock-out gene). In some embodiments of the genetically engineered hematopoietic cell comprising: (i) a modified or edited gene encoding a CD19 and (ii) a modified or edited gene encoding a CD33, the gene encoding CD33 has been modified or edited such that the gene is truncated, has inserted and/or deleted sequences (e.g., resulting in scrambled, frameshift, or nonsense sequence), or the entire gene is deleted (e.g., effectively a knock-out gene). In some embodiments of the genetically engineered hematopoietic cell comprising: (i) a modified or edited gene encoding a CD19 and (ii) a modified or edited gene encoding a CD33, the gene encoding CD19 has been modified or edited such that the entire exon 2 of CD19 is deleted or a portion of exon 2 of CD19 is deleted and the gene encoding CD33 has been modified or edited such that the CD33 gene is truncated, has inserted and/or deleted sequences (e.g., resulting in scrambled, frameshift, or nonsense sequence), or the entire CD33 gene is deleted. In some embodiments of the genetically engineered hematopoietic cell comprising: (i) a modified or edited gene encoding a CD19 and (ii) a modified or edited gene encoding a CD33, the gene encoding CD33 has been modified or edited such that the entire exon 2 of CD33 is deleted or a portion of exon 2 of CD33 is deleted and the gene encoding CD19 has been modified or edited such that the CD19 gene is truncated, has inserted and/or deleted sequences (e.g., resulting in scrambled, frameshift, or nonsense sequence), or the entire gene is deleted.

In some embodiments, the present disclosure provides a genetically engineered hematopoietic cell, comprising: (i) a gene encoding a CD19, which gene has been modified or edited such that the entire exon 2 is deleted or a portion of exon 2 is deleted and (ii) a gene encoding a CD33, which gene has been modified or edited such that the entire exon 2 is deleted or a portion of exon 2 is deleted. In some embodiments, the mutant of the CD19 antigen with exon 2 deleted or a portion of exon 2 deleted retains its biological activity. In some embodiments, the mutant of the CD19 antigen with exon 2 deleted or a portion of exon 2 deleted escapes targeting by a cytotoxic agent that targets the corresponding wild-type CD19 antigen and retains its biological activity. In some embodiments, the mutant of the CD33 antigen with exon 2 deleted or a portion of exon 2 deleted retains its biological activity. In some embodiments, the mutant of the CD33 antigen with exon 2 deleted or a portion of exon 2 deleted escapes targeting by a cytotoxic agent that targets the corresponding wild-type CD33 antigen and retains its biological activity. In some embodiments, the present disclosure provides a genetically engineered hematopoietic cell, comprising: (i) a gene encoding a CD19, which gene has been modified or edited such that the entire exon 2 is deleted or a portion of exon 2 is deleted and (ii) a gene encoding a CD33, which gene has been modified or edited such that the entire exon 2 is deleted or a portion of exon 2 is deleted. In some embodiments, the present disclosure provides a genetically engineered hematopoietic cell, comprising a gene encoding a CD19, which gene has been modified or edited such that intron 1 and/or intron 2 in CD19 has been modified or edited. In some embodiments, the genetically engineered hematopoietic cell has a sequence deletion in intron 1 and/or intron 2 of CD19 gene, e.g., either a portion of intron 1 and/or intron 2 of CD19 is deleted or the entire intron 1 and/or intron 2 of CD19 is deleted. In some embodiments, the present disclosure provides a genetically engineered hematopoietic cell, comprising a gene encoding a CD33, which gene has been modified or edited such that intron 1 and/or intron 2 in CD33 has been modified or edited. In some embodiments, the genetically engineered hematopoietic cell has a sequence deletion in intron 1 and/or intron 2 of CD33 gene, e.g., either a portion of intron 1 and/or intron 2 of CD33 is deleted or the entire intron 1 and/or intron 2 of CD33 is deleted. In some embodiments, the present disclosure provides a genetically engineered hematopoietic cell, comprising: (i) a gene encoding a CD19, which gene has been modified or edited such that intron 1 and/or intron 2 in CD19 has been modified or edited and (ii) a gene encoding a CD33, which gene has been modified or edited such that intron 1 and/or intron 2 in CD33 has been modified or edited. In some embodiments, the mutant of the CD19 antigen with intron 1 and/or intron 2 deleted or a portion of intron 1 and/or intron 2 deleted retains its biological activity. In some embodiments, the mutant of the CD19 antigen with intron 1 and/or intron 2 deleted or a portion of intron 1 and/or intron 2 deleted escapes targeting by a cytotoxic agent that targets the corresponding wild-type CD19 antigen and retains its biological activity. In some embodiments, the mutant of the CD33 antigen with intron 1 and/or intron 2 deleted or a portion of intron 1 and/or intron 2 deleted retains its biological activity. In some embodiments, the mutant of the CD33 antigen with intron 1 and/or intron 2 deleted or a portion of intron 1 and/or intron 2 deleted escapes targeting by a cytotoxic agent that targets the corresponding wild-type CD33 antigen and retains its biological activity.

Any of the genetically engineered hematopoietic cells or populations of genetically engineered hematopoietic cells described herein may be hematopoietic stem cells (HSCs). In some instances, the HSCs are CD34+/CD33− cells. Any of the hematopoietic cells described herein can be from bone marrow cells, cord blood cells, or peripheral blood mononuclear cells (PBMCs). In some embodiments, the genetically engineered hematopoietic cell is a human hematopoietic cell. In some embodiments, any of the hematopoietic cells described herein are bone marrow cells, cord blood cells, or peripheral blood mononuclear cells (PBMCs) derived from a human.

In some embodiments, the mutant of the first lineage-specific cell-surface antigen and/or the mutant of the second lineage-specific cell-surface antigen (and/or the mutant of a third, and/or fourth, and/or fifth lineage-specific cell-surface antigen) includes a mutated or deleted non-essential epitope. Such a non-essential epitope in the first lineage-specific cell surface antigen and/or the non-essential epitope in the second lineage-specific cell surface antigen (and/or the non-essential epitope in the third, and/or fourth, and/or fifth lineage-specific cell-surface antigen) has at least 3 amino acids. In some examples, the non-essential epitope in the first lineage-specific cell surface antigen and/or the non-essential epitope in the second lineage-specific cell surface antigen (and/or the non-essential epitope in the third, and/or fourth, and/or fifth lineage-specific cell-surface antigen) is 6-10 amino acids. In some examples, the non-essential epitope in the first lineage-specific cell surface antigen and/or the non-essential epitope in the second lineage-specific cell surface antigen (and/or the non-essential epitope in the third, and/or fourth, and/or fifth lineage-specific cell-surface antigen) is 6-200 amino acids. In some examples, the non-essential epitope in the first lineage-specific cell surface antigen and/or the non-essential epitope in the second lineage-specific cell surface antigen (and/or the non-essential epitope in the third, and/or fourth, and/or fifth lineage-specific cell-surface antigen) is 6-175 amino acids. In some examples, the non-essential epitope in the first lineage-specific cell surface antigen and/or the non-essential epitope in the second lineage-specific cell surface antigen (and/or the non-essential epitope in the third, and/or fourth, and/or fifth lineage-specific cell-surface antigen) is 6-150 amino acids. In some examples, the non-essential epitope in the first lineage-specific cell surface antigen and/or the non-essential epitope in the second lineage-specific cell surface antigen (and/or the non-essential epitope in the third, and/or fourth, and/or fifth lineage-specific cell-surface antigen) is 6-125 amino acids. In some examples, the non-essential epitope in the first lineage-specific cell surface antigen and/or the non-essential epitope in the second lineage-specific cell surface antigen (and/or the non-essential epitope in the third, and/or fourth, and/or fifth lineage-specific cell-surface antigen) is 6-100 amino acids. In some examples, the non-essential epitope in the first lineage-specific cell surface antigen and/or the non-essential epitope in the second lineage-specific cell surface antigen (and/or the non-essential epitope in the third, and/or fourth, and/or fifth lineage-specific cell-surface antigen) is 6-75 amino acids. In some examples, the non-essential epitope in the first lineage-specific cell surface antigen and/or the non-essential epitope in the second lineage-specific cell surface antigen (and/or the non-essential epitope in the third, and/or fourth, and/or fifth lineage-specific cell-surface antigen) is 6-50 amino acids. In some examples, the non-essential epitope in the first lineage-specific cell surface antigen and/or the non-essential epitope in the second lineage-specific cell surface antigen (and/or the non-essential epitope in the third, and/or fourth, and/or fifth lineage-specific cell-surface antigen) is 6-25 amino acids. In some examples, the non-essential epitope in the first lineage-specific cell surface antigen and/or the non-essential epitope in the second lineage-specific cell surface antigen (and/or the non-essential epitope in the third, and/or fourth, and/or fifth lineage-specific cell-surface antigen) is an entire exon or a portion of an exon.

In some embodiments at least one of the first and second lineage-specific cell-surface antigens is associated with a hematopoietic malignancy. In some embodiments at least one of any of the modified or mutant lineage-specific cell-surface antigens is associated with a hematopoietic malignancy. Non-limiting examples include CD7, CD13, CD19, CD22, CD25, CD32, CD33, CD38, CD44, CD47, CD56, 96, CD17, CD123, CD135, CD174, CLL-1, folate receptor b, IL1RAP, MUC1, NKG2D/NKG2DL, TIM-3, and WT1. In some examples, the first and second lineage-specific cell-surface antigens are selected from (a) CD19+CD33, (b) CD19+CD13, (c) CD19+CD123, (d) CD33+CD13, (e) CD33+CD123, (f) CD13+CD123.

In some embodiments, the modified lineage-specific cell-surface antigen is a type 1 lineage-specific cell-surface antigen. In some embodiments, at least one of the lineage-specific cell-surface antigens is a type 1 lineage-specific cell-surface antigen. In some embodiments, the lineage-specific cell-surface antigen is CD19. In some embodiments, at least one of the lineage-specific cell-surface antigens is CD19. In some embodiments, at least one of the first and second lineage-specific cell-surface antigens is a type 1 lineage-specific cell-surface antigen, for example, CD19. In some embodiments at least one of any of the modified or mutant lineage-specific cell-surface antigens is a type 1 lineage-specific cell-surface antigen, for example, CD19. In some embodiments, both of the first and second lineage-specific cell-surface antigens are type 1 lineage-specific cell-surface antigens. In some embodiments, the genetic modification or editing of a CD19 gene (e.g., an endogenous CD19 gene) occurs in an exon of the CD19 gene. In some embodiments, the genetic modification or editing of a CD19 gene (e.g., an endogenous CD19 gene) occurs in exon 2 of the CD19 gene. In some embodiments, the genetic modification or editing of a CD19 gene (e.g., an endogenous CD19 gene) occurs in one or more introns of the CD19 gene, e.g., including modification or editing of one or more introns that result in modification(s) in exon 2 of CD19. In some embodiments, the genetic modification or editing of a CD19 gene (e.g., an endogenous CD19 gene) results in mutation or deletion of exon 2 of a CD19 gene. In some embodiments, the genetic modification or editing of a CD19 gene (e.g., an endogenous CD19 gene) results in deletion of the entire exon 2 of a CD19 gene or deletion of a portion of exon 2 of a CD19 gene. In some instances, the mutated CD19 comprises the amino acid sequence of SEQ ID NO: 52.

In some embodiments, the genetic modification or editing of a CD19 gene (e.g., an endogenous CD19 gene) occurs in one or more introns of the CD19 gene, e.g., including modification or editing of one or more introns that result in modification(s) in exon 4 of CD19. In some embodiments, the genetic modification or editing of a CD19 gene (e.g., an endogenous CD19 gene) results in mutation or deletion of exon 4 of a CD19 gene. In some embodiments, the genetic modification or editing of a CD19 gene (e.g., an endogenous CD19 gene) results in deletion of the entire exon 4 of a CD19 gene or deletion of a portion of exon 2 of a CD19 gene. In some instances, the mutated CD19 comprises the amino acid sequence of SEQ ID NO: 73.

In some embodiments, the modified lineage-specific cell-surface antigen is a type 2 lineage-specific cell-surface antigen. In some embodiments, at least one of the lineage-specific cell-surface antigens is a type 2 lineage-specific cell-surface antigen. In some embodiments, the lineage-specific cell-surface antigen is CD33. In some embodiments, at least one of the lineage-specific cell-surface antigens is CD33. In some embodiments, at least one of the first and second lineage-specific cell-surface antigens is a type 2 lineage-specific cell-surface antigen, for example, CD33. In some embodiments at least one of any of the modified or mutant lineage-specific cell-surface antigens is a type 2 lineage-specific cell-surface antigen, for example, CD33. In some embodiments, both of the first and second lineage-specific cell-surface antigens are type 2 lineage-specific cell-surface antigens. In some embodiments, the genetic modification or editing of a CD33 gene (e.g., an endogenous CD33 gene) occurs in an exon of the CD33 gene. In some embodiments, the genetic modification or editing of a CD33 gene (e.g., an endogenous CD33 gene) occurs in exon 2 of the CD33 gene. In some embodiments, the genetic modification or editing of a CD33 gene (e.g., an endogenous CD33 gene) occurs in one or more introns of the CD33 gene, e.g., including modification or editing of one or more introns that result in modification(s) in exon 2 of CD33. In some embodiments, the genetic modification or editing of a CD33 gene (e.g., an endogenous CD33 gene) occurs in intron 1 and intron 2 of the CD33 gene. In some embodiments, the genetic modification or editing of a CD33 gene (e.g., an endogenous CD33 gene) results in mutation or deletion of exon 2 of the CD33 gene. In some embodiments, the genetic modification or editing of a CD33 gene (e.g., an endogenous CD33 gene) results in deletion of the entire exon 2 of the CD33 gene or deletion of a portion of exon 2 of the CD33 gene. In some embodiments, the genetic modification or editing of a CD33 gene (e.g., an endogenous CD33 gene) occurs in exon 3 of the CD33 gene. In some embodiments, the genetic modification or editing of a CD33 gene (e.g., an endogenous CD33 gene) occurs in one or more introns of the CD33 gene, e.g., including modification or editing of one or more introns that result in modification(s) in exon 3 of CD33. In some embodiments, the genetic modification or editing of a CD33 gene (e.g., an endogenous CD33 gene) results in mutation or deletion of exon 3 of the CD33 gene. In some embodiments, the genetic modification or editing of a CD33 gene (e.g., an endogenous CD33 gene) results in deletion of the entire exon 3 of the CD33 gene or deletion of a portion of exon 3 of the CD33 gene. In some examples, the second group of genetically engineered hematopoietic cells may contain genetic editing in exon 2 or exon 3 of a CD33 gene (e.g., including genetic modifications at one or more introns that result in modifications in exon 2 or exon 3). In some examples, the CD33 gene is an endogenous CD33 gene. Example CD33 mutants include SEQ ID NO: 56 or SEQ ID NO: 58.

In some embodiments, the second lineage-specific cell surface antigen is a type 0 protein. In some embodiments, at least one of the first and second lineage-specific cell surface antigens is a type 0 protein. In some embodiments at least one of any of the modified or mutant lineage-specific cell-surface antigens is a type 0 lineage-specific cell-surface antigen. In some embodiments, both of the first and second lineage-specific cell-surface antigens are type 0 lineage-specific cell-surface antigens. In some embodiments, the genetic modification or editing of a Type 0 antigen gene occurs in an exon of the Type 0 gene. In some embodiments, the genetic modification or editing of a Type 0 antigen occurs in exon 2 of the Type 0 antigen gene. In some embodiments, the genetic modification or editing of a Type 0 antigen gene occurs in one or more introns of the Type 0 antigen gene, e.g., including modification or editing of one or more introns that result in modification(s) in exon 2 of the Type 0 antigen gene. In some embodiments, the genetic modification or editing of a Type 0 antigen gene occurs in intron 1 and intron 2 of the Type 0 antigen gene.

Any of the genetically engineered hematopoietic cells described herein can be produced by genomic editing. In some embodiments, the genomic editing does not involve an exogenous nuclease. In some embodiments, the genomic editing involves adeno-associated virus vector mediated homologous recombination. In some embodiments, the genomic editing involves an exogenous nuclease. Exemplary approaches include the method that involve the use of a zinc finger nuclease (ZFN), a transcription activator-like effector-based nuclease (TALEN), or a CRISPR-Cas system. In some embodiments, the CRISPR-Cas system comprises a Cas endonuclease. In some embodiments, the Cas endonuclease is a Cas9 endonuclease.

In another aspect, provided herein are methods for producing any of the genetically engineered hematopoietic cells or populations of genetically engineered hematopoietic cells. In one aspect, provided herein is a method for producing a population of genetically engineered hematopoietic cells, the method comprising: (i) providing a population of hematopoietic cells, and (ii) genetically modifying or editing at least one lineage-specific cell surface antigen. In some embodiments, the at least one lineage-specific cell surface antigen is genetically modified via CRISPR to produce the population of genetically engineered hematopoietic cells. In one aspect, provided herein is a method for producing a population of genetically engineered hematopoietic cells, the method comprising: (i) providing a population of hematopoietic cells, and (ii) genetically modifying or editing a first lineage-specific cell surface antigen, or genetically modifying or editing a second lineage-specific cell surface antigen, or genetically modifying or editing a first lineage-specific cell surface antigen and a second lineage-specific cell surface antigen in the population of hematopoietic cells via CRISPR to produce the population of genetically engineered hematopoietic cells. In one aspect, provided herein is a method for producing a population of genetically engineered hematopoietic cells, the method comprising: (i) providing a population of hematopoietic cells, and (ii) genetically modifying or editing a first lineage-specific cell surface antigen and genetically modifying or editing a second lineage-specific cell surface antigen in the population of hematopoietic cells to produce the population of genetically engineered hematopoietic cells. In some embodiments, the method for producing a population of genetically engineered hematopoietic cells further comprises (iii) genetically modifying or editing one or more other lineage-specific cell surface antigen(s) in the population of hematopoietic cells to produce the population of genetically engineered hematopoietic cells. In any of these methods, the genetically engineered hematopoietic cell is a human cell.

In one aspect, provided herein is a method for producing a genetically engineered hematopoietic cell, the method comprising: (i) providing a hematopoietic cell, and (ii) genetically modifying or editing a first lineage-specific cell surface antigen, or genetically modifying or editing a second lineage-specific cell surface antigen, or genetically modifying or editing a first lineage-specific cell surface antigen and a second lineage-specific cell surface antigen in the hematopoietic cell via CRISPR to produce the genetically engineered hematopoietic cell. In one aspect, provided herein is a method for producing a genetically engineered hematopoietic cell, the method comprising: (i) providing a hematopoietic cell, and (ii) genetically modifying or editing a first lineage-specific cell surface antigen and genetically modifying or editing a second lineage-specific cell surface antigen to produce the genetically engineered hematopoietic cell. In some embodiments, the method for producing a genetically engineered hematopoietic cell further comprises (iii) genetically modifying or editing one or more other lineage-specific cell surface antigen(s) to produce the genetically engineered hematopoietic cell. In any of these methods, the genetically engineered hematopoietic cell is a human cell.

In one aspect, provided herein is a method for producing a population of genetically engineered hematopoietic cells, the method comprising: (i) providing a population of hematopoietic cells, and (ii) genetically modifying or editing a CD19 gene, or genetically modifying or editing a CD33 gene, or genetically modifying or editing a CD19 gene and a CD33 gene in the population of hematopoietic cells via CRISPR to produce the genetically engineered hematopoietic cells. In one aspect, provided herein is a method for producing a population of genetically engineered hematopoietic cells, the method comprising: (i) providing a population of hematopoietic cells, and (ii) genetically modifying or editing a CD19 gene and genetically modifying or editing a CD33 gene in the population of hematopoietic cells to produce the population of genetically engineered hematopoietic cells. In one aspect, provided herein is a method for producing a genetically engineered hematopoietic cell, the method comprising: (i) providing a hematopoietic cell, and (ii) genetically modifying or editing a CD19 gene, or genetically modifying or editing a CD33 gene, or genetically modifying or editing a CD19 gene and genetically modifying or editing a CD33 gene in the hematopoietic cell via CRISPR to produce the genetically engineered hematopoietic cell. In one aspect, provided herein is a method for producing a genetically engineered hematopoietic cell, the method comprising: (i) providing a hematopoietic cell, and (ii) genetically modifying or editing a CD19 gene and genetically modifying or editing a CD33 gene to produce the genetically engineered hematopoietic cell. In some embodiments, the method for producing a genetically engineered hematopoietic cell or population of genetically engineered hematopoietic cells further comprises (iii) genetically modifying or editing one or more other lineage-specific cell surface antigen(s) to produce the genetically engineered hematopoietic cell. In any of these methods, the genetically engineered hematopoietic cell is a human cell.

In some embodiments, the genetic editing of the CD19 gene involves one or more guide nucleic acid molecules that target one or more introns of CD19. In some embodiments, the genetic editing of the CD33 gene involves one or more guide nucleic acid molecules that target one or more introns of CD33. In some embodiments, the genetic editing of the CD33 gene involves one or more guide nucleic acid molecules that do not target the CD33 pseudogene upstream of the CD33 gene. In some embodiments, the genetic editing of the CD33 gene involves one or more guide nucleic acid molecules that (a) target one or more introns of CD33 and (b) do not target the CD33 pseudogene upstream of the CD33 gene. In some embodiments, the introns of the CD19 gene comprise intron 1 and intron 2. In some embodiments, the introns of the CD33 gene comprise intron 1 and intron 2. In some embodiments, the genetic editing of CD19 results in exclusion of exon 2 of the CD19 gene. In some embodiments, the genetic editing of CD19 results in exclusion of exon 4 of the CD19 gene. In some embodiments, the genetic editing of CD33 results in exclusion of exon 2 of the CD33 gene. In some embodiments, the genetic editing of the CD33 gene involves one or more guide nucleic acid molecules that target exon 3 of CD33. In some embodiments, the genetic editing of the CD33 gene involves at least one guide nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO: 67.

Further, provided herein is a method for producing genetically engineered hematopoietic cells, the method comprising: (i) providing a population of hematopoietic cells, and (ii) genetically editing a CD19 gene, a CD33 gene, or both a CD19 and a CD33 gene in the population of hematopoietic cells via CRISPR to produce the genetically engineered hematopoietic cells, wherein the genetic editing of the CD19 gene involves at least one guide nucleic acid molecule comprising the nucleotide sequence of SEQ ID NOs: 14-26, 67, and 69-72, and/or wherein the genetic editing of the CD33 gene involves at least one guide nucleic acid molecule comprising the nucleotide sequence of SEQ ID NOs: 27-50 and 68. In some embodiments, the method for producing genetically engineered hematopoietic cells comprises genetically editing a CD33 gene in the population of hematopoietic cells via CRISPR to produce the genetically engineered hematopoietic cells, wherein the genetic editing of the CD33 gene involves at least one guide nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO: 67.

In some embodiments, step (ii) is performed by genetic editing of both a CD19 gene and a CD33 gene in the population of hematopoietic cells via CRISPR to produce the genetically engineered hematopoietic cells. The genetic editing of the CD19 gene involves a guide nucleic acid comprising the nucleotide sequence of SEQ ID NO: 67, and/or the genetic editing of the CD33 gene involves a guide nucleic acid comprising the nucleotide sequence of SEQ ID NO: 68.

In any of the methods described herein, the hematopoietic cells can be HSCs, for example, CD34+/CD33− cells. The hematopoietic cells can be from bone marrow cells, cord blood cells, or peripheral blood mononuclear cells (PBMCs). In some embodiments, the hematopoietic cells are from human bone marrow cells, human cord blood cells, or human peripheral blood mononuclear cells (PBMCs). Also provided herein are genetically engineered hematopoietic cells having one of more of the following features:

-   -   (a) carry a genetically edited CD19 gene capable of expressing a         mutant CD19 comprising the amino acid sequence of SEQ ID NO: 52         or 73 and/or a genetically edited CD33 gene capable of         expressing a mutant CD33 comprising the amino acid sequence of         SEQ ID NO: 56 or SEQ ID NO: 58;     -   (b) carry a genetically edited CD19 gene capable of expressing a         mutant CD19 comprising the amino acid sequence of SEQ ID NO: 52         or 73 and a genetically edited CD33 gene capable of expressing a         mutant CD33 comprising the amino acid sequence of SEQ ID NO: 56;     -   (c) exon 2 of CD33 gene in the hematopoietic cell is modified         and wherein one or more portions of the CD33 pseudogene are not         modified;     -   (d) exon 2 of CD33 gene in the hematopoietic cell is deleted and         wherein one or more portions of the CD33 pseudogene are not         modified;     -   (e) exon 2 of CD33 gene in the hematopoietic cell is modified         and wherein one or more portions of the CD33 pseudogene are not         modified by deletion or mutation that causes a frameshift.     -   (f) exon 2 of CD33 gene in the hematopoietic cell is modified         and wherein the one or more portion(s) of the CD33 pseudogene         that is not modified by deletion or mutation that causes a         frameshift is selected from Exon 1, intronl, Exon 2, and         combinations thereof;     -   (g) exon 2 of CD33 gene in the hematopoietic cell is modified         and wherein the one or more portion(s) of the CD33 pseudogene         that is not modified by deletion or mutation that causes a         frameshift is selected from sequence(s) in Exon 1, intron 1,         and/or Exon 2, that share sequence homology, respectively, with         sequence(s) in Exon 1, intron 1, and/or Exon 2 of CD33.

Further, genetically engineered hematopoietic cells produced by any method disclosed herein are also within the scope of the present disclosure.

Also provided herein is a population of genetically engineered hematopoietic stem cells, wherein at least 50% (e.g., at least 60%, 70%, 75%, 80%, 85%, 90%, or 95%) of the hematopoietic stem cells therein carry both a genetically edited CD19 gene and a genetically edited CD33 gene. In some instances, the genetically edited CD19 gene is capable of expressing a CD19 mutant comprising the amino acid sequence of SEQ ID NO: 52 or 73. Alternatively or in addition, the genetically edited CD33 gene is capable of expressing a CD33 mutant comprising the amino acid sequence of SEQ ID NO: 56 or SEQ ID NO: 58.

Moreover, provided herein is a method of treating a hematopoietic malignancy (e.g., AML), comprising administering to a subject in need thereof a population of genetically engineered hematopoietic cells as disclosed herein. The method may further comprise administering to the subject an effective amount of a first immunotherapeutic agent. In some instances, the first immunotherapeutic agent is a cytotoxic agent that targets cells expressing either the first lineage-specific cell-surface antigen or the second lineage-specific cell-surface antigen.

In some examples, the first immunotherapeutic agent is a cytotoxic agent that targets cells expressing the first lineage-specific cell-surface antigen, and the method further comprises administering to the subject a second immunotherapeutic agent when the hematopoietic malignancy relapses in the subject. The second immunotherapeutic agent may be a cytotoxic agent that targets cells expressing the second lineage-specific cell-surface antigen. In one example, the first immunotherapeutic agent, the second immunotherapeutic agent, or both are CAR-T cells. In one example, the first immunotherapeutic agent, the second immunotherapeutic agent, or both are antibody drug conjugates.

The disclosure also provides methods of protecting hematopoietic stem cells from immunotherapy in a subject in need thereof, wherein the therapy targets one or more lineage-specific antigen(s). In some embodiments, the methods comprise administering a modified hematopoietic stem cell to a subject, wherein the stem cell comprises one or more gene(s) encoding the lineage-specific antigen(s) being targeted by the immunotherapy, and wherein the gene(s) are modified, mutated or edited. In some embodiments of the methods, the gene(s) are modified such that expression of the gene(s) results in modified, mutated protein(s) or complete knockout(s) of the protein or combinations thereof. In some embodiments of the method, modified, mutated protein(s) or complete knockout(s) prevent the immunotherapy from targeting the hematopoietic stem cells comprising the mutated gene(s). In some embodiments of the methods, the editing results in expression of one or more lineage-specific antigen(s), which contain a partial deletion. In some embodiments of the methods, the partial deletion compasses an entire exon or a portion of an exon. In some embodiments of the methods, the immunotherapy administered includes one or more antibody-drug conjugate(s), which can be administered concurrently or sequentially. In some embodiments of the methods, the immunotherapy administered includes cells expressing one or more chimeric antigen receptors or a pool of 2 or more cells, each expressing a different chimeric antigen receptor, which can be administered concurrently or sequentially. In one embodiment, the disclosure provides a method of protecting hematopoietic stem cells from one or more chimeric antigen receptor T cell therapies targeting one or more lineage specific antigen(s) in a subject in need thereof, wherein the hematopoietic stem cells are administered, and wherein the hematopoietic stem cells are modified such that expression of the gene(s) encoding one or more lineage specific antigen(s) result in modified, mutated forms or complete knockout(s) of the lineage specific antigen(s) targeted by the CART(s). In one embodiment of this method, the mutated form(s) of the one or more lineage specific antigen(s) lack an exon, e.g., an exon which comprises the CART or antibody-drug conjugate epitope. In any of these methods, the modified hematopoietic cell can be any of the modified hematopoietic cells described here and elsewhere herein.

Such modified hematopoietic stems cells can be generated using gene editing technologies, e.g. CRISPR, as described herein. As described elsewhere, CRISPR methodology can be used to delete a portion or an entire gene of interest. In some embodiments, CRISPR methodology can be used to delete one or more exons comprising a targeted epitope. In some instances, it is beneficial to target one or more flanking intron sequences to excise an exon. In some instances, the exon sequence itself may be targeted by CRISPR, however, current conventional CRISPR therapies may lead to small insertions and deletions, which can lead to frameshift and truncated non-functional proteins. To avoid unintentional knockouts, the intron sequences may be beneficial to target so as to more precisely edit the exon sequence of interest.

Accordingly, the disclosure also provides methods for generating modified hematopoietic stem cells, comprising introducing one or more guide RNAs capable of editing one or more gene(s) encoding one or more lineage specific antigen(s) targeted by one or more chimeric antigen receptor(s). In some embodiments of the methods, the editing results in expression of lineage specific antigen(s) lacking an exon. In some embodiments, the editing results complete knockout of lineage specific antigen(s). In some embodiments of the methods, the editing results in a combination of expression of lineage specific antigen(s) lacking an exon and complete knockout of lineage specific antigen(s) in one cell or a cell population. In some embodiments, the one or more guide RNAs are selected to target one or more introns. In some embodiments of the method, targeting of adjacent introns results in excision of the gene sequence encoding the exon between the two introns.

Targeting one intron may result in the generation of a new splice site, resulting in excision of the gene sequence encoding the adjacent exon. Exon skipping using a single guide RNA has been described (e.g., Mou et al., Genome Biology 201718:108). Accordingly, in some embodiments, one intron may be targeted according to the methods described herein.

In some embodiments, a method of protecting hematopoietic stem cells from immunotherapy may be used in a subject in need thereof, wherein the therapy targets one or more lineage-specific antigen(s). In some embodiments, the methods comprise administering a modified hematopoietic stem cell to a subject, wherein the stem cell comprises one or more gene(s) encoding the lineage-specific antigen(s) CD19 and/or CD33 being targeted by the immunotherapy, and wherein the CD19 and/or CD33 gene(s) are modified, mutated or edited. In some embodiments of the methods, the CD19 and/or CD33 gene(s) are modified such that expression result in modified, mutated CD19 and/or CD33 or complete knockout(s) of the CD19 and/or CD33 or combinations thereof. In some embodiments of the method, modified, mutated CD19 and/or CD33 protein(s) or complete CD19 and/or CD33 knockout(s) prevent the immunotherapy from targeting the hematopoietic stem cells comprising the mutated gene(s). In some embodiments of the methods, the editing results in expression CD19 and/or CD33, which contain a partial deletion. In some embodiments of the methods, the partial deletion compasses an entire exon or a portion of an exon, e.g., exon2 of CD33 and/or CD19. In some embodiments of the methods, the immunotherapy administered includes one or more antibody-drug conjugate(s) directed against CD19 and/or CD33, which can be administered concurrently or sequentially. In some embodiments of the methods, the immunotherapy administered includes cells expressing one or more chimeric antigen receptors directed against CD19 and/or CD33 or a pool of 2 cell populations, one expressing chimeric antigen receptor directed against CD19 and the other expressing a chimeric antigen receptor directed against CD33. The cells expressing chimeric antigen receptor directed against CD19 can be administered concurrently or sequentially with the cells expressing chimeric antigen receptor directed against CD33. In one embodiment, the disclosure provides a method of protecting hematopoietic stem cells from one or more chimeric antigen receptor T cell therapies targeting CD19 and/or CD33 in a subject in need thereof, wherein the hematopoietic stem cells are administered, and wherein the hematopoietic stem cells are modified such that expression of the gene(s) encoding CD19 and/or CD33 result in modified, mutated forms or complete knockout(s) of the CD19 and/or CD33. In one embodiment of this method, the mutated form(s) of CD19 and/or CD33 lack an exon, e.g., an exon which comprises the CART epitope.

Accordingly, the disclosure also provides methods for generating modified hematopoietic stem cells, comprising introducing one or more guide RNAs capable of editing one or more gene(s) encoding CD19 and/or CD33, wherein CD19 and/or CD33 are targeted by one or more chimeric antigen receptor(s) or antibody-drug conjugates. In some embodiments of the methods, the editing results in expression of CD19 and/or CD33 lacking an exon. In some embodiments, the editing results complete knockout of CD19 and/or CD33. In some embodiments of the methods, the editing results in a combination of expression of lineage specific antigen(s) lacking an exon and complete knockout of CD19 and/or CD33 in one cell or a cell population. In some embodiments, the one or more guide RNAs are selected to target one or more introns. In some embodiments of the method, targeting of adjacent introns results in excision of the gene sequence encoding the exon between the two introns.

Enumerated Embodiments

1. A population of genetically engineered hematopoietic cells, comprising:

-   -   (i) a first group of genetically engineered hematopoietic cells,         which have genetic editing in a first gene encoding a first         lineage-specific cell-surface antigen, wherein the first group         of genetically engineered hematopoietic cells (a) have reduced         or eliminated expression of the first lineage-specific         cell-surface antigen or (b) express a mutant of the first         lineage-specific cell-surface antigen; and     -   (ii) a second group of genetically engineered hematopoietic         cells, which have genetic editing in a second gene encoding a         second lineage-specific cell-surface antigen, wherein the second         group of genetically engineered hematopoietic cells (a) have         reduced or eliminated expression of the second lineage-specific         cell-surface antigen or (b) express a mutant of the second         lineage-specific cell-surface antigen.

2. The population of genetically engineered hematopoietic cells of embodiment 1, wherein the first group of genetically engineered hematopoietic cells overlaps with the second group of genetically engineered hematopoietic cells.

3. A population of genetically engineered hematopoietic cells, wherein one or more cells of the population:

-   -   (i) have reduced or eliminated expression of a first         lineage-specific cell-surface antigen relative to a wild-type         counterpart cell, or express a mutant of the first         lineage-specific cell-surface antigen; and     -   (ii) have reduced or eliminated expression of a second         lineage-specific cell-surface antigen relative to a wild-type         counterpart cell, or express a mutant of the second         lineage-specific cell-surface antigen.

4. The population of embodiment 3, wherein the reduction in expression of the first lineage-specific cell-surface antigen, second first lineage-specific cell-surface antigen, or both, is to less than or equal to 50%, 40%, 30%, 20%, 10%, 5%, 2%, or 1% of the level in a wild-type counterpart cell.

5. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein the first lineage-specific cell-surface antigen (e.g., CD19) is expressed in a primary cancer in a subject and the second lineage-specific cell-surface antigen (e.g., CD33) is expressed in a relapsed cancer in the subject.

6. The population of genetically engineered hematopoietic cells of embodiment 1 or 2, wherein the first lineage-specific cell-surface antigen (e.g., CD33) is expressed in a first sub-population of cancer cells in a subject, and the second lineage-specific cell-surface antigen (e.g., CD123 or CLL-1) is expressed in a second sub-population of cancer cells in the subject.

7. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein at least 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, or 95% of cells in the population have genetic editing (e.g., comprise an indel or comprise a deletion) at both alleles encoding the first lineage-specific cell-surface antigen.

8. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein at least 40%, 50%/0, 60%, 70%, 75%/0, 80%, 85%, 90%, or 95% of cells in the population have genetic editing (e.g., comprise an indel or comprise a deletion) at both alleles encoding the second lineage-specific cell-surface antigen.

9. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein at least 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, or 95% of cells in the population have genetic editing (e.g., comprise an indel or comprise a deletion) at both alleles encoding the first lineage-specific cell-surface antigen and at both alleles encoding the second lineage-specific cell-surface antigen.

10. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein at least 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, or 95% of copies of the first gene (encoding the lineage-specific cell-surface antigen) in the population of cells have genetic editing, e.g., as measured using PCR, e.g., according to an assay of Example 1.

11. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein at least 40%, 50%, 60%, 70%/6, 75%, 80%, 85%, 90%, or 95% of copies of the second gene (encoding the lineage-specific cell-surface antigen) in the population of cells have genetic editing, e.g., as measured using PCR, e.g., according to an assay of Example 1.

12. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein at least 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, or 95% of copies of the first and second genes (encoding the first and second lineage-specific cell-surface antigens, respectively) in the population of cells have genetic editing, e.g., as measured using PCR, e.g., according to an assay of Example 1.

13. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein at least 60%, 70%, 75%, 80%, 85%, 90%, or 95% of cells in the population (or cells differentiated from cells in the population) are negative for the first lineage-specific cell-surface antigen.

14. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein at least 60%, 70%, 75%, 80%, 85%, 90%, or 95% of cells in the population (or cells differentiated from cells in the population) are negative for the second lineage-specific cell-surface antigen.

15. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein at least 60%, 70%, 75%, 80%, 85%, 90%, or 95% of cells in the population (or cells differentiated from cells in the population) are negative for both of the first lineage-specific cell-surface antigen and the second lineage-specific cell-surface antigen.

16. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein surface levels of the first lineage-specific cell-surface antigen in the population (or cells differentiated from cells in the population) are less than 50%, 40%, 30%, 20%, 10%, 5%, 2%, or 1%6 of surface levels of the first lineage-specific cell-surface antigen in wild-type counterpart cells.

17. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein surface levels of the second lineage-specific cell-surface antigen in the population (or cells differentiated from cells in the population) are less than 50%, 40%, 30%, 20%, 10%, 5%, 2%, or 1% of surface levels of the second lineage-specific cell-surface antigen in wild-type counterpart cells.

18. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein intracellular levels of the first lineage-specific antigen in the population (or cells differentiated from cells in the population) are less than 50%, 40%, 30%, 20%, 10%, 5%, 2%, or 1% of intracellular levels of the first lineage-specific cell-surface antigen in wild-type counterpart cells.

19. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein intracellular levels of the second lineage-specific antigen in the population (or cells differentiated from cells in the population) are less than 50%, 40%, 30%, 20%, 10%, 5%, 2%, or 1% of intracellular levels of the second lineage-specific cell-surface antigen in wild-type counterpart cells.

20. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein the first and second genes are chosen from Table 1A.

21. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein the first and second lineage-specific cell-surface antigens are chosen from Table 1A.

22. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, which comprises a plurality of HSCs and/or HPCs.

23. The population of genetically engineered hematopoietic cells of embodiment 22, which retains differentiation potential, e.g., in an in vitro CFU assay, e.g., as described in Example 1 herein.

24. The population of genetically engineered hematopoietic cells of embodiment 23, wherein the cells form at least 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or 200 total colonies per 250 cells in a CFU assay, e.g., an assay of Example 1 herein.

25. The population of genetically engineered hematopoietic cells of embodiment 23 or 24, wherein the cells form at least 1, 2, 3, 4, 5, 10, or 20 CFU-GEMM colonies per 250 cells in a CFU assay, e.g., an assay of Example 1 herein.

26. The population of genetically engineered hematopoietic cells of any of embodiments 23-25, wherein the cells form at least 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 CFU-GM colonies per 250 cells in a CFU assay, e.g., an assay of Example 1 herein.

27. The population of genetically engineered hematopoietic cells of any of embodiments 23-26, wherein the cells form at least 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 BFU-E colonies per 250 cells in a CFU assay, e.g., an assay of Example 1 herein.

28. The population of genetically engineered hematopoietic cells of any of embodiments 23-27, wherein the number of BFU-E colonies is about 30%-150%, 35-135%, 40-120%, or 50%-100% of the number of CFU-GM colonies when assayed in a CFU assay (e.g., an assay of Example 1 herein).

29. The population of genetically engineered hematopoietic cells of any of embodiments 23-28, wherein the number of CFU-GEMM colonies is about 1-15%, 1-10%, or 1.5-5.0% of the number of CFU-GM colonies when assayed in a CFU assay (e.g., an assay of Example 1 herein).

30. The population of genetically engineered hematopoietic cells of any of embodiments 23-29, wherein the number of CFU-GEMM colonies is about 1-30%, 2-20%, or 3-10% of the number of BFU-E colonies when assayed in a CFU assay (e.g., an assay of Example 1 herein).

31. The population of genetically engineered hematopoietic cells of any of embodiments 23-30, wherein one, two, three, or all of:

-   -   a) the number of BFU-E colonies formed by the cells in a CFU         assay is within about 5%, 10%, 20%, or 30% of the number of         BFU-E colonies formed by otherwise similar, unmodified cells;     -   b) the number of CFU-GM colonies formed by the cells in a CFU         assay is within about 5%, 10%, 20%, or 30% of the number of         CFU-GM colonies formed by otherwise similar, unmodified cells;     -   c) the number of CFU-GEMM colonies formed by the cells in a CFU         assay is within about 5%, 10%, 20%, or 30% of the number of         CFU-GEMM colonies formed by otherwise similar, unmodified cells;         and     -   d) the total number of colonies formed by the cells in a CFU         assay is within about 5%, 10%, 20%, or 30% of the total number         of colonies formed by otherwise similar, unmodified cells.

32. The population of genetically engineered hematopoietic cells of any of embodiments 23-31, wherein the cells can give rise to differentiated myeloid cells.

33. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, which are capable of growing in culture, e.g., of increasing by at least 2, 3, 4, 5, or 10-fold (e.g., over 8 days, e.g., in conditions according to Example 1).

34. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, which have a viability of at least 50%, 60%, 70%, 75%, 80%, 85%, or 90% (e.g., after 2, 4, 6, 8, or 10 days), e.g., in conditions according to Example 1 or Example 4.

35. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, which are capable of engraftment, e.g., to produce at least 0.1%, 0.2%, 0.5%, 1%, 2%, 5%, or 10% of CD45+ cells in peripheral blood of a subject, e.g., according to an assay of Example 1.

36. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, which can produce at least 0.1%, 0.2%, 0.5%, 1%, 2%, 5%, 10%, 20%, 40%, 60%, or 80% of B cells in peripheral blood of a subject, e.g., according to an assay of Example 1.

37. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, which are resistant to a first immunotherapeutic agent that targets the first lineage-specific cell-surface antigen, e.g., wherein the ICs the first immunotherapeutic agent for the population of cells is greater than the IC₅₀ of the first immunotherapeutic agent for control cells (e.g., wherein the control cells are wild-type counterpart cells), e.g., by at least 2, 3, 4, 5, 10, 20, 50, or 100-fold. e.g., in an assay of Example 2.

38. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, which are resistant to a second immunotherapeutic agent that targets the second lineage-specific cell-surface antigen, e.g., wherein the IC₅₀ the second immunotherapeutic agent for the population of cells is greater than the IC₅₀ of the second immunotherapeutic agent for control cells (e.g., wherein the control cells are wild-type counterpart cells), e.g., by at least 2, 3, 4, 5, 10, 20, 50, or 100-fold, e.g., in an assay of Example 2.

39. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, which are resistant to a first immunotherapeutic agent that targets the first lineage-specific cell-surface antigen and a second immunotherapeutic agent that targets the second lineage-specific cell-surface antigen, e.g., wherein the cells show a specific killing of less than 50%, 40%, 35%, 30%, 25%, 20%, or 15%, e.g., in an in vitro cytotoxicity assay, e.g., in an assay of Example 9.

40. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein about 5-10%, 10-20%, 20-30%, 30-40%, 40-50%, 50-60%, 60-70%, 70-80%, or 80-90% of cells in the population substantially lack cell surface expression of both of the first lineage-specific cell-surface antigen and the second lineage-specific cell-surface antigen.

41. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein about 5-10%, 10-20%, 20-30%, 30-40%, 40-50%, 50-60%, 60-70%, 70-80%, or 80-90% of cells in the population comprise a mutation of at least one allele of the first lineage-specific cell-surface antigen and a mutation of at least one allele of the second lineage-specific cell-surface antigen.

42. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein about 5-10%, 10-20%, 20-30%, 30-40%, 40-50%, 50-60%, 60-70%, 70-80%, or 80-90% of cells in the population comprise mutations at two alleles of the first lineage-specific cell-surface antigen and mutations at two alleles of the second lineage-specific cell-surface antigen.

43. The population of genetically engineered hematopoietic cells of any of embodiments 1-42, wherein:

(a) the first lineage-specific cell-surface antigen is CD33 and the second lineage-specific cell-surface antigen is CD123; (b) the population of cells comprises HSCs; and (c) at least 20%, 30%, 40%6, 50%, or 60% of cells in the population substantially lack cell surface expression of both of CD123 and CD33.

44. The population of genetically engineered hematopoietic cells of any of embodiments 1-42, wherein:

(a) the first lineage-specific cell-surface antigen is CD33 and the second lineage-specific cell-surface antigen is CLL-1; (b) the population of cells comprises HSCs; and (c) at least 20%, 30%, 40%, 50%, or 60% of cells in the population substantially lack cell surface expression of both of CLL1 and CD33.

45. The population of genetically engineered hematopoietic cells of any of embodiments 1-42, wherein:

(a) the first lineage-specific cell-surface antigen is CD123 and the second lineage-specific cell-surface antigen is CLL-1: (b) the population of cells comprises HSCs; and (c) at least 20%, 30%, 40%, 50%, or 60% of cells in the population substantially lack cell surface expression of both of CLL1 and CD123.

46. The population of genetically engineered hematopoietic cells of any of embodiments 1-42, wherein:

(a) the first lineage-specific cell-surface antigen is CD19 and the second lineage-specific cell-surface antigen is CD33; (b) the population of cells comprises HSCs; and (c) at least 20%, 30%, 40%, 50%, or 60% of cells in the population substantially lack cell surface expression of both of CD19 and CD33.

47. The population of any of embodiments 43-46, wherein (d) the genetic editing of the first gene comprises a frameshift mutation and the genetic editing of the second gene comprises a frameshift mutation.

48. The population of genetically engineered hematopoietic cells of any of the preceding embodiments, wherein the hematopoietic cells are hematopoietic stem cells (HSCs).

49. The population of genetically engineered hematopoietic cells of embodiment 48, wherein the HSCs are CD34+/CD33− cells.

50. The population of genetically engineered hematopoietic cells of any one of embodiments 1-49, which the hematopoietic cells are from bone marrow cells, cord blood cells, or peripheral blood mononuclear cells (PBMCs).

51. The population of genetically engineered hematopoietic cells of any one of embodiments 1-40, wherein the mutant of the first lineage-specific cell-surface antigen and/or the mutant of the second lineage-specific cell-surface antigen includes a mutated non-essential epitope.

52. The population of genetically engineered hematopoietic cells of any of embodiments 1-51, wherein one or both of: the genetic editing of the gene encoding the first lineage-specific cell surface antigen comprises a frameshift mutation, and the genetic editing of the second gene comprises a frameshift mutation.

53. The population of genetically engineered hematopoietic cells of embodiment 52, wherein the frameshift mutation comprises an insertion or deletion of less than 20, 15, 10, 5, 4, 3, or 2 nucleotides.

54. The population genetically engineered hematopoietic cells of any of the preceding embodiments, wherein the genetic editing comprises genome editing.

55. The population of genetically engineered hematopoietic cells of any of embodiments 1-54, wherein one or more cells in the population are negative for one or both of the first lineage-specific cell-surface antigen and the second first lineage-specific cell-surface antigen.

56. The population of genetically engineered hematopoietic cells of any of embodiments 1-55, wherein the CD33 pseudogene is not modified in one or more (e.g., at least 50%, 60%, 70%, 80%, 85%, 90%, 95%, 98%, 99%, or all) of the cells of the population.

57. The population of genetically engineered hematopoietic cells of any of embodiments 1-56, wherein the average number of off-target genetic edits in the cell population is less than 3, 2, or 1 per cell.

58. The population of genetically engineered hematopoietic cells of embodiment 57, wherein the non-essential epitope in the first lineage-specific cell surface antigen and/or the non-essential epitope in the second lineage-specific cell surface antigen has at least 3 amino acids.

59. The population of genetically engineered hematopoietic cells of embodiment 58, wherein the non-essential epitope in the first lineage-specific cell surface antigen and/or the non-essential epitope in the second lineage-specific cell surface antigen is 6-10 amino acids.

60. The population of genetically engineered hematopoietic cells of any one of embodiments 1-59, wherein at least one of the first and second lineage-specific cell-surface antigens is a type 1 lineage-specific cell-surface antigen.

61. The population of genetically engineered hematopoietic cells of embodiment 60, wherein the type 1 lineage-specific cell-surface antigen is CD19.

62. The population of genetically engineered hematopoietic cells of embodiment 61, wherein the first group of genetically engineered hematopoietic cells contain genetic editing in exon 2 or exon 4 of a CD19 gene.

63. The population of genetically engineered hematopoietic cells of embodiment 62, wherein the CD19 gene is an endogenous CD19 gene.

64. The population of genetically engineered hematopoietic cells of embodiment 62 or 63, wherein the first group of genetically engineered hematopoietic cells express a mutated CD19 comprising the amino acid sequence of SEQ ID NO: 52 or SEQ ID NO: 73.

65. The population of genetically engineered hematopoietic cells of any one of embodiments 1-64, wherein at least one of the first and second lineage-specific cell-surface antigens is a type 2 lineage-specific cell-surface antigen.

66. The population of genetically engineered hematopoietic cells of embodiment 65, wherein the type 2 lineage-specific cell-surface antigen is CD33.

67. The population of genetically engineered hematopoietic cells of embodiment 66, wherein the second group of genetically engineered hematopoietic cells contain genetic editing in exon 2 or exon 3 of a CD33 gene.

68. The population of genetically engineered hematopoietic cells of embodiment 67, wherein the CD33 gene is an endogenous CD33 gene.

69. The population of genetically engineered hematopoietic cells of embodiment 67 or 68, wherein the second group of genetically engineered hematopoietic cells express a mutated CD33 comprising the amino acid sequence of SEQ ID NO: 56 or SEQ ID NO: 58.

70. The population of genetically engineered hematopoietic cells of any one of embodiments 1-69, which are produced by genomic editing.

71. The population of genetically engineered hematopoietic cells of embodiment 70, wherein the genome editing involves a zinc finger nuclease (ZFN), a transcription activator-like effector-based nuclease (TALEN), or a CRISPR-Cas system.

72. The population of genetically engineered hematopoietic cells of embodiment 71, wherein the CRISPR-Cas system comprises a Cas endonuclease.

73. The population of genetically engineered hematopoietic cells of embodiment 72, wherein the Cas endonuclease is a Cas9 endonuclease.

74. The population of genetically engineered hematopoietic cells of any one of embodiments 1-73, wherein at least one of the first and second lineage-specific cell-surface antigens is associated with a hematopoietic malignancy.

75. The population of genetically engineered hematopoietic cells of any one of embodiments 1-74, wherein at least one of the first and second lineage-specific cell surface antigens is a type 0 protein.

76. The population of genetically engineered hematopoietic cells of any one of embodiments 1-75, wherein the first and second lineage-specific cell surface antigens are selected from the group consisting of CD7, CD13, CD19, CD20, CD22, CD25, CD32, CD33, CD38, CD44, CD45, CD47, CD56, 96, CD117, CD123, CD135, CD174, CLL-1, folate receptor b, IL1RAP, MUC1, NKG2D/NKG2DL, TIM-3, and WT1.

77. The population of genetically engineered hematopoietic cells of embodiment 76, wherein the first and second lineage-specific cell surface antigens are selected from the group consisting of:

-   -   (i) CD19 and CD33;     -   (ii) CD19 and CD13;     -   (iii) CD19 and CD123;     -   (iv) CD19 and CLL-1;     -   (v) CD33 and CD13;     -   (vi) CD33 and CD123;     -   (vii) CD33 and CLL-1;     -   (viii) CD13 and CD123;     -   (ix) CD123 and CLL-1;     -   (x) CD19, CD33, and CD13;     -   (xi) CD19, CD33, and CD123;     -   (xii) CD33, CD13, and CD123;     -   (xiii) CD19, CD13, and CD123;     -   (xiv) CLL-1, CD123, and CD33; or     -   (xv) CD19, CD33, CD13, and CD123.

78. A method for producing genetically engineered hematopoietic cells, the method comprising:

-   -   (i) providing a population of hematopoietic cells, and     -   (ii) genetically editing a first gene encoding a first         lineage-specific cell-surface antigen and a second gene encoding         a second lineage-specific cell-surface antigen in the population         of hematopoietic to produce the genetically engineered         hematopoietic cells.

79. The method of embodiment 78, wherein the first gene and the second gene are:

-   -   (i) CD19 and CD33;     -   (ii) CD19 and CD13;     -   (iii) CD19 and CD123;     -   (iv) CD19 and CLL-1;     -   (v) CD33 and CD13;     -   (vi) CD33 and CD123;     -   (vii) CD33 and CLL-1;     -   (viii) CD13 and CD123; or     -   (ix) CD123 and CLL-1.

80. A method for producing genetically engineered hematopoietic cells, the method comprising:

-   -   (i) providing a population of hematopoietic cells, and     -   (ii) genetically editing a CD19 gene, a CD33 gene, or both genes         in the population of hematopoietic cells via CRISPR to produce         the genetically engineered hematopoietic cells,     -   wherein the genetic editing of the CD19 gene involves one or         more guide nucleic acid molecules that target one or more         introns of CD19; and     -   wherein the genetic editing of the CD33 gene involves one or         more guide nucleic acid molecules that (a) target one or more         introns of CD33; and/or (b) do not target the CD33 pseudogene         upstream of the CD33 gene.

81. The method of embodiment 80, wherein the introns of the CD19 gene comprise intron 1 and intron 2, and/or the introns of the CD33 gene comprise intron 1 and intron 2.

82. The method of embodiment 80 or 81, wherein the genetic editing of CD19 results in exclusion of exon 2 of the CD19 gene; and/or the genetic editing of CD33 results in exclusion of exon 2 of the CD33 gene.

83. A method for producing genetically engineered hematopoietic cells, the method comprising:

-   -   (i) providing a population of hematopoietic cells, and     -   (ii) genetic editing a CD19 gene, a CD33 gene, or both in the         population of hematopoietic cells via CRISPR to produce the         genetically engineered hematopoietic cells,     -   wherein the genetic editing of the CD19 gene involves at least         one guide nucleic acid molecule comprising the nucleotide         sequence of SEQ ID NOs: 14-26, 67, and 69-72, and/or     -   wherein the genetic editing of the CD33 gene involves at least         one guide nucleic acid molecule comprising the nucleotide         sequence of SEQ ID NOs: 27-50 and 68.

84. The method of embodiment 83, wherein step (ii) is performed by genetic editing both a CD19 gene and a CD33 gene in the population of hematopoietic cells via CRISPR to produce the genetically engineered hematopoietic cells,

-   -   wherein the genetic editing of the CD19 gene involves a guide         nucleic acid comprising the nucleotide sequence of SEQ ID NO:         67, and     -   wherein the genetic editing of the CD33 gene involves a guide         nucleic acid comprising the nucleotide sequence of SEQ ID NO:         68.

85. The method of any one of embodiments 80-84, wherein the hematopoietic cells are HSCs.

86. The method of embodiment 85, wherein the HSCs are CD34+/CD33− cells.

87. The method of any one of embodiment 80-86, wherein the hematopoietic cells are from bone marrow cells, cord blood cells, or peripheral blood mononuclear cells (PBMCs).

88. Genetically engineered hematopoietic cells produced by any one of embodiments 80-87.

89. A genetically engineered hematopoietic cell, which carries a genetically edited CD19 gene capable of expressing a mutant CD19 comprising the amino acid sequence of SEQ ID NO: 52 or 73, and/or a genetically edited CD33 gene capable of expressing a mutant CD33 comprising the amino acid sequence of SEQ ID NO: 56 or SEQ ID NO: 58.

90. The genetically engineered hematopoietic cell of embodiment 89, which carries a genetically edited CD19 gene capable of expressing a mutant CD19 comprising the amino acid sequence of SEQ ID NO: 52 or 73, and a genetically edited CD33 gene capable of expressing a mutant CD33 comprising the amino acid sequence of SEQ ID NO: 56.

91. A population of genetically engineered hematopoietic stem cells, wherein at least 50% of the hematopoietic stem cells therein carry both a genetically edited CD19 gene and a genetically edited CD33 gene.

92. The population of genetically engineered hematopoietic stem cells of embodiment 91, wherein the genetically edited CD19 gene is capable of expressing a CD19 mutant comprising the amino acid sequence of SEQ ID NO: 52 or 73, and/or the genetically edited CD33 gene is capable of expressing a CD33 mutant comprising the amino acid sequence of SEQ ID NO: 56 or SEQ ID NO:58.

93. A genetically engineered hematopoietic cell, wherein exon 2 of CD33 gene in the hematopoietic cell is modified and wherein the CD33 pseudogene is not modified.

94. The genetically engineered hematopoietic cell of embodiment 93, wherein exon 2 of CD33 gene in the hematopoietic cell is deleted.

95. The genetically engineered hematopoietic cell of embodiment 93 or 94, wherein the CD33 pseudogene is not modified by deletion or mutation that causes a frameshift.

96. The genetically engineered hematopoietic cell of embodiment 93 or 94, wherein the CD33 pseudogene is not modified by deletion or mutation that causes a frameshift in exon 1, intron 1, exon 2, or a combination thereof.

97. The genetically engineered hematopoietic cell of embodiment 93, wherein the frameshift is in sequence(s) in exon 1, intron 1, and/or exon 2 of the CD33 pseudogene that share sequence homology, respectively, with sequence(s) in exon 1, intron 1, and/or exon 2 of CD33.

98. A method of supplying hematopoietic cells to a subject (e.g., a subject having a hematopoietic malignancy), comprising:

-   -   (a) providing a population of genetically engineered         hematopoietic cells of any one of embodiments 1-77 and 88-97,         wherein optionally the genetically engineered hematopoietic         cells comprise HSCs and/or HPCs; and     -   (b) administering the population of genetically engineered         hematopoietic cells to the subject, e.g., under conditions that         allow for engraftment of at least a portion of the population,     -   thereby supplying the hematopoietic cells to the subject.

99. A method of treating a hematopoietic malignancy, comprising administering to a subject in need thereof a population of genetically engineered hematopoietic cells of any one of embodiments 1-77 and 88-97.

100. The method of embodiment 99, which further comprises:

-   -   (a) administering to the subject an effective amount of a first         immunotherapeutic agent that targets the first lineage-specific         cell-surface antigen, and     -   (b) administering to the subject an effective amount of a second         immunotherapeutic agent that targets the second lineage-specific         cell-surface antigen.

101. The method of embodiment 100, wherein the first immunotherapeutic agent and the second immunotherapeutic agent are administered simultaneously or sequentially (e.g., sequentially with or without overlap, e.g., wherein the first and second immunotherapeutic agent are not present in the subject at the same time).

102. The method of embodiment 100 or 101, wherein the first immunotherapeutic agent is administered when the subject has a primary cancer, and the second immunotherapeutic is administered when the subject has a relapsed cancer or cancer that is resistant to the first immunotherapeutic agent.

103. The method of embodiment 102, wherein the primary cancer is AML and the relapsed cancer is relapsed AML.

104. The method of embodiment 102, wherein the primary cancer is AML and the relapsed cancer is ALL.

105. The method of any of embodiments 102 or 104, wherein the relapsed cancer underwent a lineage switch relative to the primary cancer.

106. The method of any of embodiments 102-105, wherein the first lineage-specific cell surface antigen is absent in the relapsed cancer, or is expressed at a lower level in the relapsed cancer compared to the primary cancer (e.g., at less than 50%, 40%, 30%, 20%, or 10% of the protein level in the primary cancer), or is expressed in fewer cancer cells in the relapsed cancer compared to the primary cancer (e.g., less than 50%, 40%, 30%, 20%, or 10% the relapsed cancer cells detectably express the protein).

107. The method of any of embodiments 102-106, wherein the primary cancer comprises one or more resistant cells, e.g., cells that lack the first lineage-specific cell surface antigen or express it at a lower level than in sensitive cells.

108. The method of any of embodiments 89-107, which further comprises: administering to the subject an effective amount of a first immunotherapeutic agent that targets expressing the first lineage-specific cell-surface antigen.

109. The method of embodiment 108, wherein, if the subject experiences relapse (e.g., a relapse wherein the cancer is negative for the first lineage-specific cell surface antigen), then administering to the subject an effective amount of a second immunotherapeutic agent that targets the second lineage-specific cell-surface antigen.

110. The method of any of embodiments 100-109, wherein the first lineage-specific cell-surface antigen is CD19 and the second lineage-specific cell-surface antigen is CD33.

111. The method of any of embodiments 100-110, wherein the subject has a cancer (e.g., a primary cancer) that comprises a first sub-population of cancer cells and a second sub-population of cancer cells.

112. The method of embodiment 111, wherein the first sub-population of cancer cells expresses the first lineage-specific cell-surface antigen and the second sub-population of cancer cells expresses the second lineage-specific cell-surface antigen.

113. The method of embodiment 112, wherein the first sub-population of cancer cells is targeted by the first immunotherapeutic agent and the second sub-population of cancer cells is targeted by the second immunotherapeutic agent.

114. The method of embodiment 113, wherein the first sub-population of cancer cells is resistant to the second immunotherapeutic agent, or wherein the second immunotherapeutic agent is less effective against the first sub-population of cancer cells than against the second sub-population of cancer cells, e.g., by about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%.

115. The method of embodiment 113 or 114, wherein the second sub-population of cancer cells is resistant to the first immunotherapeutic agent, or wherein the first immunotherapeutic agent is less effective against the second sub-population of cancer cells than against the first sub-population of cancer cells, e.g., by about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%.

116. The method of any of embodiments 113-115, wherein the first sub-population of cancer cells does not express the second lineage-specific cell surface antigen, or the second lineage-specific cell surface antigen is expressed at a lower level in the first sub-population compared to the second sub-population (e.g., at less than 50%, 400%, 30%, 20%, or 10% of the protein level).

117. The method of any of embodiments 113-116, wherein the second sub-population of cancer cells does not express the first lineage-specific cell surface antigen, or the first lineage-specific cell surface antigen is expressed at a lower level in the second sub-population compared to the first sub-population (e.g., at less than 50%, 40%, 30%, 20%, or 10% of the protein level).

118. The method of any of embodiments 113-117, wherein the first sub-population of cancer cells expresses CD33 and the second sub-population of cancer cells expresses CD123 or CLL-1.

119. The method of any of embodiments 113-118, wherein the first sub-population of cancer cells is about 50-99%, 60-90%, 70-90%, or about 80% of cancer cells in the subject.

120. The method of any of embodiments 113-119, wherein the second sub-population of cancer cells is about 1-50%, 10-40%, 10-30%, or about 20% of cancer cells in the subject.

121. The method of any of embodiments 113-120, wherein the first sub-population of cancer cells are bulk cancer cells and/or the second sub-population of cancer cells are cancer stem cells.

122. The method of any of embodiments 113-121, wherein the first sub-population of cancer cells have one or more markers of differentiated hematopoietic cells and/or the second sub-population of cancer cells have one or more markers of HSCs or HPCs.

123. The method of any of embodiments 113-122, wherein the first immunotherapeutic agent and the second immunotherapeutic agent are administered simultaneously.

124. The method of any of embodiments 113-123, wherein the first immunotherapeutic agent and the second immunotherapeutic agent are administered such that both of the first immunotherapeutic agent and the second immunotherapeutic agent are present in the subject at the same time.

125. The method of any of embodiments 113-124, further comprising administering to the subject an effective amount of a first immunotherapeutic agent.

126. The method of embodiment 125, wherein the first immunotherapeutic agent is a cytotoxic agent that targets cells expressing either the first lineage-specific cell-surface antigen or the second lineage-specific cell-surface antigen.

127. The method of embodiment 126, wherein the first immunotherapeutic agent is a cytotoxic agent that targets cells expressing the first lineage-specific cell-surface antigen, and the method further comprises administering to the subject a second immunotherapeutic agent when the hematopoietic malignancy relapses in the subject.

128. The method of embodiment 127, wherein the second immunotherapeutic agent is a cytotoxic agent that targets cells expressing the second lineage-specific cell-surface antigen.

129. The method of any one of embodiments 126-128, wherein the first immunotherapeutic agent, the second immunotherapeutic agent, or both are CAR-T cells.

130. The method of any one of embodiments 126-128, wherein the first immunotherapeutic agent, the second immunotherapeutic agent, or both are antibodies.

131. The method of any one of embodiments 126-128, wherein the first immunotherapeutic agent, the second immunotherapeutic agent, or both are antibody-drug conjugates.

132. The method of any one of embodiments 113-131, wherein the hematopoietic malignancy is AML.

133. The method of embodiment 132, wherein the AML is relapsed AML.

The details of one or more embodiments of the invention are set forth in the description below. Other features or advantages of the present invention will be apparent from the following drawings and detailed description of several embodiments, and also from the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present disclosure, which can be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.

FIGS. 1A and 1B are schematic illustrations showing an example therapeutic process involving the methods described herein. 1A: The process includes the steps of obtaining CD34+ cells (obtained from a donor or autologously), genetically engineering the CD34+ cells, engrafting the engineered cells into a patient, performing CAR T cell therapy on the patient, resulting in cleared or reduced cancer burden and retained hematopoiesis. 1B: An engineered donor CD34+ cell in which the non-essential epitope of a lineage-specific cell-surface antigen is modified such that it does not bind a CAR T cell that is specific for an epitope of the lineage-specific cell-surface antigen.

FIG. 2 is a schematic of the extracellular and transmembrane portions of the lineage-specific cell-surface protein human CD33. Regions of CD33 that are predicted to be less deleterious when modified are indicated by the boxes. The sequence corresponds to SEQ ID NO: 51.

FIGS. 3A and 3B are schematic illustrations showing CAR T cells bind to cells expressing human CD33 but not to cells expressing human CD33 in which an epitope of CD33 has been modified or deleted. 3A: CAR T cells targeting CD33+ acute myeloid leukemia cells leading to cell lysis. 3B: CAR T cells are not able to bind to genetically engineered donor graft cells in which an epitope of CD33 has been modified or deleted. As a result, these cells do not undergo lysis.

FIG. 4 is a schematic of CRISPR/Cas9-mediated genomic deletion of CD19 exon 2, resulting in expression of a CD19 variant having exon 2 deleted.

FIGS. 5A and 5B include diagrams showing investigation of various modified single guide RNAs (ms-sgRNAs) targeting CD19 in a human leukemic cell line (K562 cells). 5A: photos showing PCR amplicons derived from the region spanning introns 1 and 2 of the CD19 gene as determined by T7E1 assays. Samples were either treated (+) or untreated (−) with T7E1. The percentage cleavage efficiency is indicated under each lane. C=New England Biolabs (NEB) Sample Control, WT=wild-type untransfected cells, Cas9=Cas9 only. 5B: a chart showing the percent INDEL determined by T7E1 assays and TIDE analysis.

FIGS. 6A-6C include diagrams showing dual ms-sgRNA-mediated deletion of exon 2 of CD19 in K562 cells. 6A: a schematic showing a PCR-based assay to detect CRISPR/Cas9-mediated genomic deletion of exon 2 of CD19 via dual ms-sgRNA-mediated CRISPR/Cas9. 6B: a photo showing deletion of the region between exon 1 and exon 3 after treating K562 cells with indicated pairs of ms-sgRNAs by an end-point PCR assay of genomic DNA, 6C: a chart showing the percentage deletion quantitated by end-point PCR.

FIGS. 7A and 7B include diagrams showing screening of CD19 ms-sgRNAs targeting introns 1 or 2 in CD34⁺ HSCs by T7E1 assay and TIDE analysis. 7A: a photo showing PCR amplicons derived from the region spanning introns 1 and 2 of the CD19 gene as determined by T7E1 assays. Samples were either treated (+) or untreated (−) with T7E1. The percent insertion/deletion (INDEL) and cleavage efficiency are indicated under each lane. C=NEB Sample Control, Cas9=Cas9 only. 7B: PCR amplicons derived from the region spanning introns 1 and 2 of the CD19 gene were analyzed by T7E1 Assay or TIDE analysis, and the percent INDEL was determined. Cas9=cas9 only control.

FIGS. 8A and 8B include diagrams showing dual ms-sgRNA-mediated deletion of CD19 exon 2 in CD34+ HSCs. 8A: a photo showing the smaller deletion PCR product compared to the larger parental band as determined by PCR across the genomic deletion region. 8B: a chart showing the percent deletion quantified by end-point PCR.

FIGS. 9A and 9B include diagrams showing investigation of ms-sgRNAs targeting introns 1 or 2 of CD19 in CD34+ HSCs. 9A: a photo showing PCR amplicons derived from the region spanning introns 1 and 2 of the CD19 gene as determined by T7E1 assays. The percent cleavage efficiency is indicated under each lane. 9B: a chart showing PCR amplicons derived from the region spanning introns 1 and 2 of the CD19 gene as analyzed by T7E1 assay, and the percent INDEL. Cas9=cas9 only control.

FIGS. 10A-10D include diagrams showing efficient dual ms-sgRNA-mediated deletion of exon 2 of CD19in CD34+ HSCs. 10A: a photo showing the smaller deletion PCR product compared to the larger parental band as determined by PCR across the genomic deletion region. The percent deletion is indicated under each lane. 10B: a chart showing the percent deletion quantified by end-point PCR. 10C: is a photo showing PCR products of full-length CD19 or CD19 with deletion of exon 2 when edited using the pair of gRNA6/gRNA14. 10D: a chart showing percentage of CFUs of cells edited by the gRNA6/gRNA14 pair. BFU-E: burst forming unit-erythroid; CFU-GM: colony forming unit-granulocyte/macrophage; CFU-GEMM: colony forming unit of multipotential myeloid progenitor cells (generate granulocytes, erythrocytes, monocytes, and megakaryocytes.

FIGS. 11A-11E are diagrams showing production and characterization of B-cell lymphoma cells having exon 2 deletion in CD19 using a pair of gRNAs, gRNA6 and gRNA14. 11A: photos showing PCR products of genomic DNA of full-length CD19 and CD19 with exon 2 deletion (left panel) and cDNA of full-length CD19 and CD19 with exon 2 deletion. 11B: charts showing quantification of editing efficiency by end-point PCR. 11C: a photo showing expressing of full-length CD19 and CD19 mutant with deletion of fragment encoded by exon 2 using an antibody specific to the C-terminus of CD19. 11D: charts showing surface and intracellular staining of CD19-expressing in edited cells as measured by flow cytometry. 11E: charts showing cell number (left panel) and cell viability (right panel) of Raji B-cells expressing CD19exon2.

FIGS. 12A-12C include diagrams illustrating engraftment of CD19ex2 hematopoietic stem cells (HSCs) in a mouse model. 12A: a schematic work flow to assess differentiation potential of edited CD34+ HSCs. d=days, w=weeks, w/o=week old, RNP=ribonucleoprotein. 12B: a chart showing percentage of CD45+ cells in peripheral blood collected from mice engrafted with HSCs expressing CD19ex2. 12C: a chart showing percentage of CD19 B cells in peripheral blood collected from mice engrafted with HSCs expressing CD19ex2.

FIG. 13 is a schematic work flow to assess in vivo selectivity and efficacy of CART19 therapy in a Raji Burkitt's lymphoma tumor model. d=days, w-weeks, w/o=week old.

FIGS. 14A-14D includes diagrams showing the generation of Raji-fluc-GFP cells in which exon 2 of CD19 has been deleted. 14A: diagrams showing expression of CD19 in Raji-fluc-GFP cell lines transfected with the indicated combinations of ms-sgRNAs as determined by FACS. Parental Raji cells and Raj-fluc-GFP nucleofected with Cas9 only are included as controls. 14B: is a chart showing the percentage of live cells in each population of cells (CD19 “hi,” CD19 “int,” and CD19 “lo”). 14C: is a photo showing the smaller PCR product for the exon 2 deletion compared to the larger parental band as determined by PCR across the genomic deletion region. 14D: is a chart showing the percentage of cells having a deleted exon 2 of CD19 in the bulk population of cells as determined by end-point PCR.

FIGS. 15A-15B includes diagrams showing the level of CART19 cytotoxicity against Raji cells in which CD19 exon 2 has been deleted. 15A: a line graph showing that cells in which exon 2 of CD19 has been deleted are resistant to CART19 cytotoxicity. 15B: a bar graph showing that cells in which exon 2 of CD19 has been deleted are resistant to CART 19 cytotoxicity.

FIG. 16 is a schematic showing an exemplary in vivo model assessing the efficacy and selectivity of a CART therapeutic paired with edited HSCs involving the methods described herein.

FIG. 17 is a schematic showing CD33 exon 2 editing, resulting in expression of the CD33m variant.

FIGS. 18A-18B include charts showing investigation of various ms-sgRNAs targeting introns 1 or 2 of CD33 in CD34+ HSCs by TIDE analysis. PCR amplicons derived from the region spanning introns 1 and 2 of the CD33 gene were analyzed by TIDE analysis and the percent INDEL was determined. 18A: guide RNAs 1-19. 18B: guide RNAs 10-24.

FIGS. 19A-19B include diagrams showing characterization of CD33-edited primary CD34+ HSCs. 19A: a diagram showing flow cytometric analysis of CD34+ HSCs, either unedited (left panel, mock (“NT”)) or edited producing a full CD33 knockout (middle panel, “CD33 gRNA KO”), or edited with the CD33 gRNA-18/gRNA-24 pair resulting in the expression of a mutated CD33 with exon 2-encoded fragment deleted (CD33ex2) or producing a full knock out (right panel, “CD33 gRNA 18+24”), 19B: a chart showing the percentage of HSCs having CD33 knocked out (“KO”) and CD33 with exon 2 deletion (“ex2 Del”) obtained in cells edited by knock-out gRNA or the CD33 gRNA18/gRNA24 pair.

FIGS. 20A-20B include diagrams showing genotyping and in vitro differentiation of cells edited by dual gRNAs targeting CD33. 20A: a chart showing that CD33ex2 cells and CD33KO cells retained differentiation potential in vitro, as determined by a CFU assay. 20B: a photo showing that both CD33ex2 and knock-out alleles were observed in differentiated myeloid cells treated with the CD33 gRNA18/gRNA24 pair.

FIGS. 21A-21C include diagrams showing generation and characterization of CD33ex2 in AML cell lines. 21A: a photo showing genomic PCR results of selected HL60 clones resulting from gene editing with the CD33 gRNA18/gRNA24 pair. 21B: a diagram illustrating Taqman assays of total CD33 (Full-length+ex2del, including both full-length and exon 2 deletion) and CD33 (with exon 2 deletion). 21C: charts showing the expression level of total CD33 (full-length and exon 2 deletion; left panel) and the expression level of CD33ex2del in Jurkat cells, parent HL60 cells, and a number of edited HL60 clones.

FIGS. 22A-22C include diagrams showing susceptibility of CD33ex2 cells to gemtuzumab ozogamicin (GO). 22A: chart showing viability of cancer cell lines (Jurkat, THP-1, and HL-60) treated with GO at the indicated concentrations. 22B: chart showing viability of THP-1 cells, CD33ex2 THP-1 cells (generated using CD33 gRNA18/gRNA24 pair), HL-60 cells, and CD33ex2 HL-60 cells (generated using CD33 gRNA18/gRNA24 pair) treated with GO at the indicated concentrations. 22C: chart showing viability of wild-type HSCs, CD33KO HSCs, and CD33ex2 HSCs (generated using CD33 gRNA18/gRNA24 pair) post-GO treatment (“GO”) as compared to PBS control (“PBS”).

FIGS. 23A-23D include diagrams showing that CD33ex2 cells are resistant to CART33-mediated cytotoxicity. 23A: a chart showing the level of cell lysis of wild-type HL-60 cells (CD33⁺) in the presence of CART33 (expressing anti-CD33 CAR1). 23B: a chart showing the level of cell lysis of CD33ex2 HL-60 cells in the presence of CART33. 23C: a chart showing the level of cell lysis of CD33KO HL-60 cells in the presence of CART33. 23D: a chart comparing the percentage of cell lysis of CD33+ cells, CD33ex2 cells, and CD33KO cells in the presence of CART33, at the indicated cell ratios.

FIGS. 24A-24D include diagrams showing the results of a TIDE assay showing efficient multiplex genomic editing of both CD19 and CD33. 24A: a chart showing genomic editing of CD19, CD33, and CD19+CD33 in NALM-6 cells. 24B: a chart showing genomic editing of CD19, CD33, and CD19+CD33 in HSCs. 24C: a chart showing genomic editing of CD19, CD33, and CD19+CD33 in HL-60 cells. 24D: a chart showing genomic editing of CD19, CD33, and both CD19 and CD33 in NALM-6 cells.

FIGS. 25A-25C include diagrams showing the results of a nucleofection assay showing the effect of multiplex genomic editing of both CD19 and CD33 on viability in HSCs and cell lines as compared to single RNA nucleofection. The gRNAs used in the nucleofections are indicated on the x-axis. 25A: a chart showing percent viability of HSC cells following genome editing. 25B: a chart showing percent viability of Nalm-6 cells following genome editing. From left to right, each set of three bars corresponds to zero, 24 h, and 48 h. 25C: a chart showing percent viability of HL-60 cells following genome editing. From left to right, each set of four bars corresponds to zero, 48 h, 96 h, and 7 d.

FIGS. 26A-26C include diagrams showing sequences and bar graphs of a TIDE analysis of NALM-6 cells transfected with CD19-19 gRNA/RNP and CD33-37 gRNA/RNP complexes. 26A: a schematic of sequences identified and the relative contribution of each sequence for the CD19 edited Nalm-6 cells. 26B: a schematic of sequences identified and the relative contribution of each sequence for the CD33 edited Nalm-6 cells. 26C: a chart showing the frequency of INDELS that are +/−1 and +/−2 (left columns and right columns, respectively, for each gene). The TIDE analysis indicates most INDELS are small insertions.

FIG. 27 is a schematic showing the sequence of the CD33 locus including cut sites for CD33 gRNA-24 and gRNA-18. In this figure, the sequence gtgagtggctgtggggagag is labeled gRNA-24 and the sequence ttcatgggtactgcagggca is labeled gRNA-18.

FIG. 28 shows an experimental schematic and results showing the editing efficiency achieved in CD34+ HSCs using control (“Mock,” Cas9 only), CD33 knockout (“CD33KO,” CD33 gRNA-37), CD33 exon2 deletion (“CD33ex2del.” CD33 gRNA18 and gRNA-24). The editing efficiency (percentage modification) of the CD33 knockout was assessed by TIDE analysis, and % INDEL was determined. The fraction population with a deletion of exon 2 was determined by end-point PCR. For the CD33 exon2 deletion edited cells, the deletion efficiency of 30% refers to the editing events that resulted in deletion of exon 2, but does not include the events that resulted in a complete knockout of CD33.

FIG. 29 includes a diagram showing analysis of editing events in HSCs resulting from use of CD33 gRNA-37. TIDE analysis shows the percentage of sequences observed for each INDEL obtained by editing CD34+ HSCs using gRNA37.

FIG. 30 includes a diagram showing the results of flow cytometric analysis of unstained cells, unedited (“Mock”), and HSCs edited using CD33 gRNA-37.

FIGS. 31A-31E include diagrams and a table showing analysis of populations of CD34+HSCs edited with either CD33 gRNA-37 or the CD33 gRNA-18 and gRNA-24 pair, at various times following treatment with gemtuzumab ozogamicin (GO). 31A: a line graph showing the number of cells in each of the indicated populations following GO treatment over time. 31B: a table showing results corresponding to the graph shown in FIG. 31A. 31C: a photograph showing analysis of CD33 editing following treatment with gemtuzumab ozogamicin. Percentage of edited cells in the sample edited using CD33 gRNA37 (“KO”) was assessed by TIDE analysis, and the percentage of edited cells in the sample edited using CD333 gRNA-18 and gRNA-24 (“CD33ex2del”) was assessed by deletion PCR. 31D: a chart showing the percent CD14+ cells (myeloid differentiation) in the indicated cell populations in the absence of gemtuzumab ozogamicin over time as indicated. 31E: a chart showing the percent CD14+ cells (myeloid differentiation) in the indicated cell populations following treatment gemtuzumab ozogamicin over time as indicated.

FIGS. 32A and 32B include photographs showing genomic editing of CD19 in the NAM6 cell line transfected with control (“WT,” wildtypeiunmodified), CD19 sgRNA 6 and sgRNA-14 pair (“Ex2del-1”), CD19 sgRNA-7 and sgRNA-16 pair (“Ex2del-2”), CD19 sgRNA-23 and sgRNA-24 pair (CD19 knock out; “CD19KO”). 32A: a photograph of a Western blot with an antibody recognizing the Ig-like C2-type domain encoded by CD19 exon 4 in the indicated cell populations. 32B: a photograph of a Western blot with an antibody recognizing the C-terminus of CD19 in the indicated cell populations.

FIG. 33 shows target expression on AML cell lines. The expression of CD33, CD123 and CLL1 in MOLM-13 and THP-1 cells and an unstained control was determined by flow cytometric analysis. The X-axis indicates the intensity of antibody staining and the Y-axis corresponds to number of cells.

FIG. 34 shows CD33- and CD123-modified MOLM-13 cells. The expression of CD33 and CD123 in wild-type (WT), CD33^(−/−), CD123^(−/−) and CD33^(−/−) CD123^(−/−) MOLM-13 cells was assessed by flow cytometry. For the generation of CD33^(−/−) or CD123^(−/−) MOLM-13 cells, WT MOLM-13 cells were electroporated with CD33- or CD123-targeting RNP, followed by flow cytometric sorting of CD33- or CD123-negative cells, CD33^(−/−)CD123^(−/−) MOLM-13 cells were generated by electroporating CD33^(−/−) cells with CD123-targeting RNP and sorted for CD123-negative population. The X-axis indicates the intensity of antibody staining and the Y-axis corresponds to number of cells.

FIG. 35 shows an in vitro cytotoxicity assay of CD33 and CD123 CAR-Ts. Anti-CD33 CAR-T and anti-CD123 CAR-T were incubated with wild-type (WT), CD33^(−/−), CD123^(−/−) and CD33^(−/−) CD123^(−/−) MOLM-13 cells, and cytotoxicity was assessed by flow cytometry. Non-transduced T cells were used as mock CAR-T control. The CARpool group was composed of 1:1 pooled combination of anti-CD33 and anti-CD123 CAR-T cells. Student's t test was used. ns=not significant; *P<0.05; **P<0.01. The Y-axis indicates the percentage of specific killing.

FIG. 36 shows CD33- and CLL 1-modified HL-60 cells. The expression of CD33 and CLL1 in wild-type (WT), CD33^(−/−), CLL1^(−/−) and CD33^(−/−) CLL^(−/−) HL-60 cells was assessed by flow cytometry. For the generation of CD33^(−/−) or CLL1^(−/−) HL-60 cells, WT HL-60 cells were electroporated with CD33- or CLL1-targeting RNP, followed by flow cytometric sorting of CD33- or CLL 1-negative cells, CD33^(−/−)CLL1^(−/−) HL-60 cells were generated by electroporating CD33^(−/−) cells with CLL1-targeting RNP and sorted for CLL1-negative population. The X-axis indicates the intensity of antibody staining and the Y-axis corresponds to number of cells.

FIG. 37 shows an in vitro cytotoxicity assay of CD33 and CLL1 CAR-Ts. Anti-CD33 CAR-T and anti-CLL1 CAR-T were incubated with wild-type (WT), CD33^(−/−), CLL^(−/−) and CD33^(−/−) CLL1^(−/−) HL-60 cells, and cytotoxicity was assessed by flow cytometry. Non-transduced T cells were used as mock CAR-T control. The CARpool group was composed of 1:1 pooled combination of anti-CD33 and anti-CLL1 CAR-T cells. Student's t test was used. ns=not significant; *P<0.05; **P<0.01, ***P<0.001, ****P<0.0001. The Y-axis indicates the percentage of specific killing.

FIG. 38 shows gene-editing efficiency of CD34+ cells. Human CD34+ cells were electroporated with Cas9 protein and CD33-, CD123- or CLL1-targeting gRNAs, either alone or in combination. Editing efficiency of CD33, CD123 or CLL1 locus was determined by Sanger sequencing and TIDE analysis. The Y-axis indicates the editing efficiency (% by TIDE).

FIGS. 39A-39C shows in vitro colony formation of gene-edited CD34+ cells. Control or CD33, CD123, CLL-1-modified CD34+ cells were plated in Methocult 2 days after electroporation and scored for colony formation after 14 days. BFU-E: burst forming unit-erythroid: CFU-GM: colony forming unit-granulocyte/macrophage; CFU-GEMM: colony forming unit of multipotential myeloid progenitor cells (generate granulocytes, erythrocytes, monocytes, and megakaryocytes). Student's t test was used.

DETAILED DESCRIPTION OF THE INVENTION

Successfully identifying suitable proteins for targeted cancer therapies presents a significant challenge. Many potential target proteins are present on both the cell surface of a cancer cell and on the cell surface of normal, non-cancer cells, which may be required or critically involved in the development and/or survival of the subject. Many of the target proteins contribute to the functionality of such essential cells. Thus, therapies targeting these proteins may lead to deleterious effects in the subject, such as significant toxicity and/or other side effects. Further, resistance to CAR-T therapy remains a challenge in treatment of hematopoietic malignance, such as acute myeloid leukemia (AML) due to switch of cancer antigens on cancer cells, thereby escaping CAR-T therapy. For example, patients having B-cell acute lymphoblastic leukemia (B-ALL) were found to develop acute myeloid leukemia (AML) with CD19⁻ cancer cells after CAR-T therapy.

The present disclosure provides methods, cells, compositions, and kits aimed at addressing at least the above-stated problems. The methods, cells, compositions, and kits described herein provide a safe and effective treatment for hematological malignancies, allowing for targeting of one or more lineage-specific cell surface proteins (e.g., type 0, type 1, or type 2 proteins) that are present not only on cancer cells but also on cells critical for the development and/or survival of the subject.

More specifically, hematopoietic cells as described herein can be used (for example) in the treatment of a subject that receives two or more different therapies for cancer. Many therapies deplete the subject's endogenous, non-cancerous hematopoietic cells. Replacement or rescue hematopoietic cells described herein can replace the subject's depleted immune cells. Two particular examples of this method are described below.

First, in some cases, a subject receives the first therapy (e.g., against CD19), and then the cancer relapses, and then the subject receives the second therapy (e.g., against CD33). The present application provides, e.g., rescue cells that are resistant to both therapies. Thus, the rescue cells can be administered to the subject at or near the time of the first therapy, and if relapse occurs, the subject can then receive the second therapy without depleting the rescue cells.

Second, in some cases, a subject may need to receive two therapies at once, e.g., because the cancer comprises two sub-populations of cells (e.g., one expressing CD33 and the second expressing CD123 and/or CLL-1), and each therapy only attacks one of the sub-populations. As described herein, rescue cells resistant to both therapies can replace the subject's depleted immune cells even in the presence of both therapies.

Experimental evidence provided in the working Examples herein demonstrates the production, viability, differentiation potential, and resistance to therapy of various cells edited at two antigens. For instance, Examples 3 and 4 show a high frequency of multiplex editing of CD19 and CD33 HSC cells, without impairing viability. Example 9 shows a high frequency of editing of other pairs of cell surface antigens, e.g., CD33 and CD123, CD33 and CLL1, and CD123 and CLL1. Example 9 also shows that doubly edited cells show resistance to CART targeting the antigens.

The present disclosure also provides a population of rescue hematopoietic cells that comprises a first sub-population of cells that is (and/or gives rise to) cells resistant to a first therapy and a second sub-population of cells that is (and/or gives rise to) cells resistant to a second therapy. (Optionally, the population can comprise cells that are (and/or give rise to) cells resistant to both therapies: however this is not required in this embodiment). The cell populations can be useful, e.g., when subjects are treated with two therapies sequentially. For instance, in some embodiments, the edited cell-surface antigens are antigens that are typically not expressed in normal HSCs, but become expressed in later lineages, so the transplanted HSCs are resistant to both therapies regardless of whether any HSCs are edited for both antigens. This population of HSCs will continue to produce differentiated cells, some of which are deficient for the first antigen, and some of which are deficient for the second antigen. When the subject is treated with the first therapy, differentiated cells deficient for the first antigen will survive, and when the subject is treated with the second therapy, differentiated cells deficient for the second antigen will survive. Thus, such heterogeneous populations of cells can be useful as rescue cells.

Accordingly, described herein are genetically engineered hematopoietic cells such as hematopoietic stem cells (HSCs) having genetic editing in one or more genes coding for lineage-specific cell-surface proteins, for example, CD33 and/or CD19; methods of producing such, for examples, via the CRISPR approach using specific guide RNAs; and methods of treating a hematopoietic malignancy using the engineered hematopoietic cells, either taken alone, or in combination with one or more cytotoxic agents (e.g., CAR-T cells) that can target the wild-type lineage-specific cell-surface antigens but not those encoded by the edited genes in the engineered hematopoietic cells.

I. Genetically Engineered Hematopoietic Cells

The present disclosure provides genetically engineered hematopoietic cells such as hematopoietic stem cells that carry genetically edited genes for reducing or eliminating expression of one or more lineage-specific cell-surface antigens, or for expressing the one or more lineage-specific cell-surface antigens in mutated form. The mutated antigens would retain at least partial bioactivity of the antigens but can escape targeting by cytotoxic agents such as CAR-T cells specific to the antigens. In some embodiments, the lineage-specific cell-surface antigens of interest may not be expressed on hematopoietic cells such as HSCs in nature. However, such antigens may be expressed on cells differentiated from the HSCs (e.g., descendants thereof). “Expressing a lineage-specific cell-surface protein” or “expressing a lineage-specific cell-surface antigen” means that at least a portion of the lineage-specific cell-surface protein, or antigen thereof, can be detected on the surface of the hematopoietic cells or descendants thereof. As used herein, “descendants” of hematopoietic cells include any cell type or lineage of cells that arise from the hematopoietic cells. In some embodiments, the descendants of the hematopoietic cells are a cell type or lineage of cells that have differentiated from the hematopoietic cells.

The genetically engineered hematopoietic cells may be used alone for treating hematopoietic malignancies, or in combination with one or more cytotoxic agents that target the wild-type lineage-specific cell-surface antigens but not the mutant encoded by the edited genes in the genetically engineered hematopoietic cells. Such hematopoietic cells, upon differentiation, could compensate the loss of function caused by elimination of functional non-cancerous cells due to immunotherapy that targets lineage-specific cell-surface antigen(s), which may also expressed on normal cells. This approach would also broaden the choice of target proteins for immunotherapy such as CART therapy. For example, certain lineage-specific cell-surface proteins (e.g., Type 0 antigen) are essential to the development and/or survival of essential cells/tissue and thus are poor target in conventional immunotherapy. Being compensated by the genetically engineered hematopoietic stem cells described herein, such lineage-specific cell-surface proteins (e.g., Type 0 antigen) could also be suitable targets of immunotherapy, when it is combined with the engineered HSCs.

(A) Genetically Engineered Hematopoietic Cells Expressing Multiple Lineage-Specific Cell Surface Antigens in Mutated Form

In some embodiments, provided herein are a population of genetically engineered hematopoietic cells such as HSCs, which collectively carry genetically edited genes of at least two lineage-specific cell-surface proteins. The genetically edited genes express the antigens in mutated form, e.g., having one or more non-essential epitopes deleted or mutated so as to escape recognition (e.g., have a reduced binding activity) by cytotoxic agents specific to the antigens. Deletion or mutation of a non-essential epitope in a lineage-specific cell-surface protein is not expected to dramatically affect the biological activity of such an antigen.

In some instances, the hematopoietic cell population (e.g., HSCs) described herein can be homogenous, including cells each carrying multiple genetically edited genes (e.g., 2, 3, or 4) of lineage-specific cell-surface antigens. In other instances, the hematopoietic cell population is heterogeneous, comprising (a) cells that carry a genetically edited gene encoding a first lineage-specific cell-surface antigen, (b) cells that carry a genetically edited gene encoding a second lineage-specific cell-surface antigen (which is different from the first antigen), and/or (c) cells that carrying genetically edited genes of both the first and second lineage-specific cell-surface antigens.

In some embodiments, the population of cells obtained post editing comprises cells that have one or more of the target genes partially or completely deleted or both. In some embodiments, the population of cells obtained post editing comprise cells which have gene(s) encoding one or more lineage-specific antigen(s) which are edited such that expression results in a lineage-specific antigen(s) having a partial sequence deletion, e.g., lacking one or more exon(s) of the lineage-specific antigen, and cells comprising edited gene(s) which result in a complete KO of the lineage-specific antigen. In some embodiments, the population of cells obtained post editing comprise cells which have gene(s) encoding one or more lineage-specific antigen(s) which are edited such that expression results in a lineage-specific antigen(s) having a partial sequence deletion, e.g., lacking one or more exon(s) of the lineage-specific antigen, and also have edited gene(s) which result in a complete KO of the lineage-specific antigen.

In some embodiments, the population of cells obtained post editing comprise cells which have gene(s) encoding CD19 and/or CD33 which are edited such that expression results in a CD19 and/or CD33 having a partial sequence deletion, e.g., lacking one or more exon(s) of CD19 and/or CD33, and cells comprising edited CD19 and/or CD33 gene(s) which result in a complete KO of the lineage-specific antigen. In some embodiments, the population of cells obtained post editing comprise cells which have gene(s) encoding CD19 and/or CD33 which are edited such that expression results in a CD19 and/or CD33 polypeptide having a partial sequence deletion, e.g., lacking one or more exon(s) of CD19 and/or CD33, and also have edited gene(s) which result in a complete KO of CD19 and/or CD33.

Lineage-Specific Cell-Surface Proteins

As used herein, the terms “protein,” “peptide,” and “polypeptide” may be used interchangeably and refer to a polymer of amino acid residues linked together by peptide bonds. In general, a protein may be naturally occurring, recombinant, synthetic, or any combination of these. Also within the scope of the term are variant proteins, which comprise a mutation (e.g., substitution, insertion, or deletion) of one or more amino acid residues relative to the wild-type counterpart.

As used herein, the terms “lineage-specific cell-surface protein” and “cell-surface lineage-specific protein” may be used interchangeably and refer to any protein that is to sufficiently present on the surface of a cell and is associated with one or more populations of cell lineage(s). For example, the protein may be present on one or more populations of cell lineage(s) and absent (or at reduced levels) on the cell-surface of other cell populations. In some embodiments, the terms lineage-specific cell-surface antigen” and “cell-surface lineage-specific antigen” may be used interchangeably and refer to any antigen of a lineage-specific cell-surface protein.

In general, lineage-specific cell-surface proteins can be classified based on a number of factors, such as whether the protein and/or the populations of cells that present the protein are required for survival and/or development of the host organism. A summary of exemplary types of lineage-specific proteins is provide in Table 1 below.

TABLE 1 Classification of Lineage Specific Proteins Type of Lineage Specific Protein Characteristics of the Lineage Specific Protein Type 0 a) protein is required for survival of an organism, and b) cell type carrying type 0 protein is required for survival of an organism and is not unique to a tumor, or tumor-associated virus Type 1 a) protein is not required for survival of an organism, and b) cell type carrying type 1 protein is not required for survival of an organism Type 2 a) protein is not required for survival of an organism, and b) cell type carrying type 2 protein is required for the survival of an organism Type 3 a) protein is not required for the survival of an organism; b) cell type carrying protein is not required for survival of an organism; and c) The protein is unique to a tumor, or a tumor associated virus An example is the LMP-2 protein in EBV infected cells, including EBV infected tumor cells (Nasopharyngeal carcinoma and Burkitts Lymphoma)

As shown in Table 1, type 0 lineage-specific cell-surface proteins are necessary for the tissue homeostasis and survival, and cell types carrying type 0 lineage-specific cell-surface protein may be also necessary for survival of the subject. Thus, given the importance of type 0 lineage-specific cell-surface proteins, or cells carrying type 0 lineage-specific cell-surface proteins, in homeostasis and survival, targeting this category of proteins may be challenging using conventional CAR T cell immunotherapies, as the inhibition or removal of such proteins and cell carrying such proteins may be detrimental to the survival of the subject. Consequently, lineage-specific cell-surface proteins (such as type 0 lineage-specific proteins) and/or the cell types that carry such proteins may be required for the survival, for example because it performs a vital non-redundant function in the subject, then this type of lineage specific protein may be a poor target for conventional CAR T cell based immunotherapies.

However, by combining the genetically engineered hematopoietic stem cells described herein and cytotoxic agent such as CAR-T cell-based therapy, the selection of target antigen can be expanded to essential antigens such as type 0 lineage-specific cell-surface proteins. In some embodiments, the engineered hematopoietic cells (e.g., HSCs) have one or more genes of type 0 antigens edited for expression of these type 0 antigens in mutated form, which retain (at least partially) bioactivity of the type 0 antigens but can escape targeting by type 0 antigen-specific cytotoxic agents such as CAR-T cells so as to remedy the loss of normal cells expressing the type 0 antigens due to the therapy.

In contrast to type 0 proteins, type 1 cell-surface lineage-specific proteins and cells carrying type 1 cell-surface lineage-specific proteins are not required for tissue homeostasis or survival of the subject. Targeting type 1 cell-surface lineage-specific proteins is not likely to lead to acute toxicity and/or death of the subject. For example, as described in Elkins et al. (Mol. Cancer Ther. (2012) 10:2222-32) a CAR T cell engineered to target CD307, a type 1 protein expressed uniquely on both normal plasma cells and multiple myeloma (MM) cells would lead to elimination of both cell types. However, since the plasma cell lineage is expendable for the survival of the organism, CD307 and other type 1 lineage specific proteins are proteins that are suitable for CAR T cell based immunotherapy. Lineage specific proteins of type 1 class may be expressed in a wide variety of different tissues, including, ovaries, testes, prostate, breast, endometrium, and pancreas.

In some embodiments, the genetically engineered hematopoietic cells (e.g., HSCs) have one or more genes of type 1 antigens for expression of the type 1 proteins in mutated forms, which retain (at least partially) bioactivity of the type 1 antigens but can escape targeting by type 1 antigen-specific cytotoxic agents such as CAR-T cells. Use of such engineered HSCs (either alone or in combination with cytotoxic agents such as CAR-T cells targeting the type 1 antigens) may improve the longer-term survival and quality of life of the patient. For example, targeting all plasma cells, while not expected to lead to acute toxicity and/or death, could have longer-term consequences such as reduced function of the humoral immune system leading to increased risk of infection.

Targeting type 2 proteins presents a significant difficulty as compared to type 1 proteins. Type 2 proteins are those characterized where: (1) the protein is dispensable for the survival of an organism (i.e., is not required for the survival), and (2) the cell lineage carrying the protein is indispensable for the survival of an organism (i.e., the particular cell lineage is required for the survival). For example, CD33 is a type 2 protein expressed in both normal myeloid cells as well as in Acute Myeloid Leukemia (AML) cells (Dohner et al., NEJM 373:1136 (2015)). As a result, a CAR T cell engineered to target CD33 protein could lead to the killing of both normal myeloid cells as well as AML cells, which may be incompatible with survival of the subject.

In some embodiments, the genetically engineered hematopoietic cells (e.g., HSCs) have one or more genes of type 2 antigens for expression of the type 2 antigens in mutated form, which retain (at least partially) bioactivity of the type 2 antigens but can escape targeting by type 1 antigen-specific cytotoxic agents such as CAR-T cells. Use of such engineered HSCs (either alone or in combination with cytotoxic agents such as CAR-T cells targeting the type 2 antigens) may improve the longer-term survival and quality of life of the patient. For example, targeting all plasma cells, while not expected to lead to acute toxicity and/or death, could have longer-term consequences such as reduced function of the humoral immune system leading to increased risk of infection.

In some embodiments, the cell-surface lineage-specific protein is BCMA, CD19, CD20, CD30, ROR1, B7H6, B7H3, CD23, CD38, C-type lectin like molecule-1, CS1, IL-5, L1-CAM, PSCA, PSMA, CD138, CD133, CD70, CD7, CD13, NKG2D. NKG2D ligand, CLEC12A, CD11, CD123, CD56, CD34, CD14, CD33, CD66b, CD41, CD61, CD62, CD235a, CD146, CD326, LMP2, CD22, CD52, CD10, CD3/TCR, CD79/BCR, and CD26. In some embodiments, the cell-surface lineage-specific protein is CD33 or CD19.

Alternatively or in addition, the cell-surface lineage-specific protein may be a cancer protein, for example a cell-surface lineage-specific protein that is differentially present on cancer cells. In some embodiments, the cancer protein is a protein that is specific to a tissue or cell lineage. Examples of cell-surface lineage-specific protein that are associated with a specific type of cancer include, without limitation, CD20, CD22 (Non-Hodgkin's lymphoma, B-cell lymphoma, chronic lymphocytic leukemia (CLL)), CD52 (B-cell CLL), CD33 (Acute myelogenous leukemia (AML)), CD10 (gp100) (Common (pre-B) acute lymphocytic leukemia and malignant melanoma), CD3/T-cell receptor (TCR) (T-cell lymphoma and leukemia), CD79/B-cell receptor (BCR) (B-cell lymphoma and leukemia), CD26 (epithelial and lymphoid malignancies), human leukocyte antigen (HLA)-DR, HLA-DP, and HLA-DQ (lymphoid malignancies), RCAS 1 (gynecological carcinomas, biliary adenocarcinomas and ductal adenocarcinomas of the pancreas) as well as prostate specific membrane antigen. In some embodiments, the cell-surface protein CD33 and is associated with AML cells.

In some embodiments, the genetically engineered HSCs may have edited genes which encode at least two (e.g., two, three, or four) lineage-specific cell-surface proteins, which can be selected from CD7, CD13, CD19, CD22, CD20, CD25, CD32, CD33, CD38, CD44, CD45, CD47, CD56, 96, CD117, CD123, CD135, CD174, CLL-1, folate receptor 3, IL1RAP, MUC1, NKG2D/NKG2DL, TIM-3, and WT1. In specific examples, the genetically engineered HSCs may have edited genes of the following combinations: (a) CD19+CD33, (b) CD19+CD13, (c) CD19+CD123, (d) CD33+CD13, (e) CD33+CD123, (f) CD13+CD123, (g) CD19+CD33+CD13, (h) CD19+CD33+CD123, (i) CD19+CD13+CD123, (j) CD33+CD13+CD123, or (k) CD19+CD33+CD13+CD123. In some embodiments, the genetically engineered HSCs may have edited genes which encode CD33 and one or more lineage-specific cell-surface proteins selected from CD7, CD13, CD19, CD22, CD20, CD25, CD32, CD33, CD38, CD44, CD45, CD47, CD56, 96, CD117, CD123, CD135, CD174, CLL-1, folate receptor β, IL1RAP, MUC1, NKG2D/NKG2DL, TIM-3, and WT1.

In some embodiments, one or both of the lineage-specific cell surface proteins are chosen from CD1a, CD1b, CD1c, CD1d, CD1e, CD2, CD3, CD3d, CD3e, CD3g, CD4, CD5, CD6, CD7, CD8a, CD8b, CD9, CD10, CD11a, CD11b, CD11c, CD11d, CDw12, CD13, CD14, CD15, CD16, CD16b, CD17, CD18, CD19, CD20, CD21, CD22, CD23, CD24, CD25, CD26, CD27, CD28, CD29, CD30, CD31, CD32a, CD32b, CD32c, CD33, CD34, CD35, CD36, CD37, CD38, CD39, CD40, CD41, CD42a, CD42b, CD42c, CD42d, CD43, CD44, CD45, CD45RA, CD45RB, CD45RC, CD45RO, CD46, CD47, CD48, CD49a, CD49b, CD49c, CD49d, CD49e, CD49f, CD50, CD51, CD52, CD53, CD54, CD55, CD56, CD57, CD58, CD59, CD60a, CD61, CD62E, CD62L, CD62P, CD63, CD64a, CD65, CD65s, CD66a, CD66b, CD66c, CD66F, CD68, CD69, CD70, CD71, CD72, CD73, CD74, CD75, CD75S, CD77, CD79a, CD79b, CD80, CD81, CD82, CD83, CD84, CD85A, CD85C, CD85D, CD85E, CD85F, CD85G, CD85H, CD85I, CD85J, CD85K, CD86, CD87, CD88, CD89, CD90, CD91, CD92, CD93, CD94, CD95, CD96, CD97, CD98, CD99, CD99R, CD100, CD101, CD102, CD103, CD104, CD105, CD106, CD107a, CD107b, CD108, CD109, CD110, CD111, CD112, CD113, CD114, CD115, CD116, CD117, CD118, CD19, CD120a, CD120b, CD121a, CD121b, CD121a CD121b, CD122, CD123, CD124, CD125, CD126, CD127, CD129, CD130, CD131, CD132, CD133, CD134, CD135, CD136, CD137, CD138, CD139, CD140a, CD140b, CD141, CD142, CD143, CD14, CDw145, CD146, CD147, CD148, CD150, CD152, CD152, CD153, CD154, CD155, CD156a, CD156b, CD156c, CD157, CD158b1, CD158b2, CD158d, CD158e1/e2, CD158f, CD158g, CD158h, CD158i, CD158j, CD158k, CD159a, CD159c, CD160, CD161, CD163, CD164, CD165, CD166, CD167a, CD168, CD169, CD170, CD171, CD172a, CD172b, CD172g, CD173, CD174, CD175, CD175s, CD176, CD177, CD178, CD179a, CD179b, CD180, CD181, CD182, CD183, CD184, CD185, CD186, CD191, CD192, CD193, CD194, CD195, CD196, CD197, CDw198, CDw199, CD200, CD201, CD202b, CD203c, CD204, CD205, CD206, CD207, CD208, CD209, CD210a, CDw210b, CD212, CD213a1, CD213a2, CD215, CD217, CD218a, CD218b, CD220, CD221, CD222, CD223, CD224, CD225, CD226, CD227, CD228, CD229, CD230, CD231, CD232, CD233, CD234, CD235a, CD235b, CD236, CD236R, CD238, CD239, CD240, CD241, CD242, CD243, CD244, CD245, CD246, CD247, CD248, CD249, CD252, CD253, CD254, CD256, CD257, CD258, CD261, CD262, CD263, CD264, CD265, CD266, CD267, CD268, CD269, CD270, CD272, CD272, CD273, CD274, CD275, CD276, CD277, CD278, CD279, CD280, CD281, CD282, CD283, CD284, CD286, CD288, CD289, CD290, CD292, CDw293, CD294, CD295, CD296, CD297, CD298, CD299, CD300a, CD300c, CD300e, CD301, CD302, CD303, CD304, CD305, CD306, CD307a, CD307b, CD307c, CD307d, CD307e, CD309, CD312, CD314, CD315, CD316, CD317, CD318, CD319, CD320, CD321, CD322, CD324, CD325, CD326, CD327, CD328, CD329, CD331, CD332, CD333, CD334, CD335, CD336, CD337, CD338, CD339, CD340, CD344, CD349, CD350, CD351, CD352, CD353, CD354, CD355, CD357, CD358, CD359, CD360, CD361, CD362 and CD363.

In some embodiments, one or both of the lineage-specific cell surface proteins are chosen from CD19; CD123: CD22: CD30; CD171; CS-1 (also referred to as CD2 subset 1, CRACC, SLAMF7, CD319, and 19A24); C-type lectin-like molecule-1 (CLECL1); CD33; epidermal growth factor receptor variant III (EGFRvIII); ganglioside G2 (CD2); ganglioside GD3 (aNeu5Ac(2-8)aNeu5Ac(2-3)bDGalp(1-4)bDGlep(1-1)Cer); TNF receptor family member B cell maturation (BCMA), Tn antigen ((Tn Ag) or (GalNAc.alpha.-Ser/Thr)); prostate-specific membrane antigen (PSMA); Receptor tyrosine kinase-like orphan receptor 1 (ROR1): Fms-Like tyrosine Kinase 3 (FLT3); Tumor-associated glycoprotein 72 (TAG72); CD38: CD44v6; Carcinoembrvonic antigen (CEA): Epithelial cell adhesion molecule (EPCAM); B7H3 (CD276); KIT (CD117): Interleukin-13 receptor subunit alpha-2 (IL-13Ra2 or CD213A2); Mesothelin; Interleukin 11 receptor alpha (IL-11Ra); prostate stem cell antigen (PSCA): Protease Serine 21 (Testisin or PRSS21); vascular endothelial growth factor receptor 2 (VEGFR2): Lewis(Y) antigen; CD24; Platelet-derived growth factor receptor beta (PDGFR-beta); Stage-specific embryonic antigen-4 (SSEA-4); CD20; Folate receptor alpha; Receptor tyrosine-protein kinase ERBB2 (Her2/neu); Mucin 1, cell surface associated (MUC1); epidermal growth factor receptor (EGFR); neural cell adhesion molecule (NCAM); Prostase: prostatic acid phosphatase (PAP): elongation factor 2 mutated (ELF2M): Ephrin B2; fibroblast activation protein alpha (FAP): insulin-like growth factor I receptor (IGF-I receptor), carbonic anhydrase IX (CAIX), Proteasome (Prosome, Macropain) Subunit, Beta Type 9 (LMP2): glycoprotein 100 (gp 100); oncogene fusion protein consisting of breakpoint cluster region (BCR) and Abelson murine leukemia viral oncogene homolog 1 (Abl) (bcr-abl); tyrosinase; ephrin type-A receptor 2 (EphA2); Fucosyl GMI; sialyl Lewis adhesion molecule (sLe): ganglioside GM3 (aNeu5Ac(2-3)bDGalp(1-4)bDGlcp(1-1)Cer): transglutaminase 5 (TGS5); high molecular weight-melanoma-associated antigen (HMWMAA); o-acetyl-GD2 ganglioside (OAcGD2); Folate receptor beta; tumor endothelial marker 1 (TEM1/CD248); tumor endothelial marker 7-related (TEM7R); claudin 6 (CLDN6); thyroid stimulating hormone receptor (TSHR); G protein-coupled receptor class C group 5, member D (GPRC5D); chromosome X open reading frame 61 (CXORF61); CD97: CD179a: anaplastic lymphoma kinase (ALK); Polysialic acid; placenta-specific 1 (PLAC 1): hexasaccharide portion of globoH glycoceramide (GloboH): mammary gland differentiation antigen (NY-BR-1); uroplakin 2 (UPK2): Hepatitis A virus cellular receptor 1 (HAVCR1); adrenoceptor beta 3 (ADRB3): pannexin 3 (PANX3); G protein-coupled receptor 20 (GPR20); lymphocyte antigen 6 complex: locus K 9 (LY6K): Olfactory receptor 51E2 (OR51E2); TCR Gamma Alternate Reading Frame Protein (TARP): Wilms tumor protein (WT1); Cancer/testis antigen 1 (NY-ESO-1): Canceritestis antigen 2 (LAGE-1a): Melanoma-associated antigen 1 (MAGE-A1), ETS translocation-variant gene 6, located on chromosome 12p (ETV6-AML): sperm protein 17 (SPA17); X Antigen Family, member 1A (XAGEI); angiopoietin-binding cell surface receptor 2 (Tie 2); melanoma cancer testis antigen-1 (MAD-CT-1): melanoma cancer testis antigen-2 (MAD-CT-2): Fos-related antigen 1; tumor protein p53 (p53): p53 mutant: prostein: surviving; telomerase: prostate carcinoma tumor antigen-1 (PCTA-1 or Galectin 8), melanoma antigen recognized by T cells 1 (MelanA or MARTI); Rat sarcoma (Ras) mutant; human Telomerase reverse transcriptase (hTERT); sarcoma translocation breakpoints: melanoma inhibitor of apoptosis (ML-1AP); ERG (transmembrane protease, serine 2 (TMPRSS2) ETS fusion gene); N-Acetyl glucosaminyl-transferase V (NA 17); paired box protein Pax-3 (PAX3): Androgen receptor; Cyclin B 1; v-myc avian myelocytomatosis viral oncogene neuroblastoma derived homolog (MYCN); Ras Homolog Family Member C (RhoC); Tyrosinase-related protein 2 (TRP-2): Cytochrome P450 1B1 (CYP1B1): CCCTC-Binding Factor (Zinc Finger Protein)-Like (BORIS or Brother of the Regulator of Imprinted Sites), Squamous Cell Carcinoma Antigen Recognized By T Cells 3 (SART3): Paired box protein Pax-5 (PAX5): proacrosin binding protein sp32 (OY-TES1); lymphocyte-specific protein tyrosine kinase (LCK): A kinase anchor protein 4 (AKAP-4); synovial sarcoma, X breakpoint 2 (SSX2); Receptor for Advanced Glycation Endproducts (RAGE-1); renal ubiquitous 1 (RU1); renal ubiquitous 2 (RU2); legumain; human papilloma virus E6 (HPV E6): human papilloma virus E7 (HPV E7); intestinal carboxy esterase; heat shock protein 70-2 mutated (mut hsp70-2); CD79a; CD79b; CD72; Leukocyte-associated immunoglobulin-like receptor 1 (LAIR1); Fc fragment of IgA receptor (FCAR or CD89); Leukocyte immunoglobulin-like receptor subfamily A member 2 (LILRA2); CD300 molecule-like family member f(CD300LF); C-type lectin domain family 12 member A (CLEC12A); bone marrow stromal cell antigen 2 (BST2); EGF-like module-containing mucin-like hormone receptor-like 2 (EMR2), lymphocyte antigen 75 (LY75); Glypican-3 (GPC3); Fc receptor-like 5 (FCRL5): and immunoglobulin lambda-like polypeptide 1 (IGLL 1).

In some embodiments, one or both of the lineage-specific cell surface proteins are chosen from CD11a, CD18, CD19, CD20, CD31, CD34, CD44, CD45, CD47, CD51, CD58, CD59, CD63, CD97, CD99, CD100, CD1002, CD123, CD127, CD133, CD135, CD157, CD172b, CD217, CD300a, CD305, CD317, CD321, CD33, and CLL1.

In some embodiments, one or both of the lineage-specific cell surface proteins are chosen from CD33, CD123, CLL1, CD38, CD135 (FLT3), CD56 (NCAM1), CD117 (c-KIT), FRβ (FOLR2), CD47, CD82, TNFRSF1B (CD120B), CD191, CD96, PTPRJ (CD148), CD70, LILRB2 (CD85D), CD25 (IL2Ralpha), CD44, CD96, NKG2D Ligand, CD45, CD7, CD15, CD19, CD20, CD22, CD37, and CD82.

In some embodiments, one or both of the lineage-specific cell surface proteins are chosen from CD7, CD11a, CD15, CD18, CD19, CD20, CD22, CD25, CD31, CD33, CD34, CD37, CD38, CD44, CD45, CD47, CD51, CD56, CD58, CD59, CD63, CD70, CD82, CD85D, CD96, CD97, CD99, CD100, CD102, CD117, CD120B, CD123, CD127, CD133, CD135, CD148, CD157, CD172b, CD191, CD217, CD300a, CD305, CD317, CD321, CLL1, FRβ (FOLR2), NKG2D Ligand.

Table 1A lists exemplary pairs of first and second lineage-specific cell surface proteins that can be used in accordance with the compositions and methods described herein.

— CD11a, CD7 CD15, CD7 CD18, CD7 CD19, CD7 CD7, CD11a — CD15, CD11a CD18, CD11a CD19, CD11a CD7, CD15 CD11a, CD15 — CD18, CD15 CD19, CD15 CD7, CD18 CD11a, CD18 CD15, CD18 — CD19, CD18 CD7, CD19 CD11a, CD19 CD15, CD19 CD18, CD19 — CD7, CD20 CD11a, CD20 CD15, CD20 CD18, CD20 CD19, CD20 CD7, CD22 CD11a, CD22 CD15, CD22 CD18, CD22 CD19, CD22 CD7, CD25 CD11a, CD25 CD15, CD25 CD18, CD25 CD19, CD25 CD7, CD31 CD11a, CD31 CD15, CD31 CD18, CD31 CD19, CD31 CD7, CD33 CD11a, CD33 CD15, CD33 CD18, CD33 CD19, CD33 CD7, CD34 CD11a, CD34 CD15, CD34 CD18, CD34 CD19, CD34 CD7, CD37 CD11a, CD37 CD15, CD37 CD18, CD37 CD19, CD37 CD7, CD38 CD11a, CD38 CD15, CD38 CD18, CD38 CD19, CD38 CD7, CD44 CD11a, CD44 CD15, CD44 CD18, CD44 CD19, CD44 CD7, CD45 CD11a, CD45 CD15, CD45 CD18, CD45 CD19, CD45 CD7, CD47 CD11a, CD47 CD15, CD47 CD18, CD47 CD19, CD47 CD7, CD51 CD11a, CD51 CD15, CD51 CD18, CD51 CD19, CD51 CD7, CD56 CD11a, CD56 CD15, CD56 CD18, CD56 CD19, CD56 CD7, CD58 CD11a, CD58 CD15, CD58 CD18, CD58 CD19, CD58 CD7, CD59 CD11a, CD59 CD15, CD59 CD18, CD59 CD19, CD59 CD7, CD63 CD11a, CD63 CD15, CD63 CD18, CD63 CD19, CD63 CD7, CD70 CD11a, CD70 CD15, CD70 CD18, CD70 CD19, CD70 CD7, CD82 CD11a, CD82 CD15, CD82 CD18, CD82 CD19, CD82 CD7, CD85D CD11a, CD85D CD15, CD85D CD18, CD85D CD19, CD85D CD7, CD96 CD11a, CD96 CD15, CD96 CD18, CD96 CD19, CD96 CD7, CD97 CD11a, CD97 CD15, CD97 CD18, CD97 CD19, CD97 CD7, CD99 CD11a, CD99 CD15, CD99 CD18, CD99 CD19, CD99 CD7, CD100 CD11a, CD100 CD15, CD100 CD18, CD100 CD19, CD100 CD7, CD102 CD11a, CD102 CD15, CD102 CD18, CD102 CD19, CD102 CD7, CD117 CD11a, CD117 CD15, CD117 CD18, CD117 CD19, CD117 CD7, CD120B CD11a, CD120B CD15, CD120B CD18, CD120B CD19, CD120B CD7, CD123 CD11a, CD123 CD15, CD123 CD18, CD123 CD19, CD123 CD7, CD127 CD11a, CD127 CD15, CD127 CD18, CD127 CD19, CD127 CD7, CD133 CD11a, CD133 CD15, CD133 CD18, CD133 CD19, CD133 CD7, CD135 CD11a, CD135 CD15, CD135 CD18, CD135 CD19, CD135 CD7, CD148 CD11a, CD148 CD15, CD148 CD18, CD148 CD19, CD148 CD7, CD157 CD11a, CD157 CD15, CD157 CD18, CD157 CD19, CD157 CD7, CD172b CD11a, CD172b CD15, CD172b CD18, CD172b CD19, CD172b CD7, CD191 CD11a, CD191 CD15, CD191 CD18, CD191 CD19, CD191 CD7, CD217 CD11a, CD217 CD15, CD217 CD18, CD217 CD19, CD217 CD7, CD300a CD11a, CD300a CD15, CD300a CD18, CD300a CD19, CD300a CD7, CD305 CD11a, CD305 CD15, CD305 CD18, CD305 CD19, CD305 CD7, CD317 CD11a, CD317 CD15, CD317 CD18, CD317 CD19, CD317 CD7, CD321 CD11a, CD321 CD15, CD321 CD18, CD321 CD19, CD321 CD7, CLL1 CD11a, CLL1 CD15, CLL1 CD18, CLL1 CD19, CLL1 CD7, FOLR2 CD11a, FOLR2 CD15, FOLR2 CD18, FOLR2 CD19, FOLR2 CD7, NKG2D CD11a, NKG2D CD15, NKG2D CD18, NKG2D CD19, NKG2D Ligand Ligand Ligand Ligand Ligand CD7, EMR2 CD11a, EMR2 CD15, EMR2 CD18, EMR2 CD19, EMR2 CD20, CD7 CD22, CD7 CD25, CD7 CD31, CD7 CD33, CD7 CD20, CD11a CD22, CD11a CD25, CD11a CD31, CD11a CD33, CD11a CD20, CD15 CD22, CD15 CD25, CD15 CD31, CD15 CD33, CD15 CD20, CD18 CD22, CD18 CD25, CD18 CD31, CD18 CD33, CD18 CD20, CD19 CD22, CD19 CD25, CD19 CD31, CD19 CD33, CD19 — CD22, CD20 CD25, CD20 CD31, CD20 CD33, CD20 CD20, CD22 — CD25, CD22 CD31, CD22 CD33, CD22 CD20, CD25 CD22, CD25 — CD31, CD25 CD33, CD25 CD20, CD31 CD22, CD31 CD25, CD31 — CD33, CD31 CD20, CD33 CD22, CD33 CD25, CD33 CD31, CD33 — CD20, CD34 CD22, CD34 CD25, CD34 CD31, CD34 CD33, CD34 CD20, CD37 CD22, CD37 CD25, CD37 CD31, CD37 CD33, CD37 CD20, CD38 CD22, CD38 CD25, CD38 CD31, CD38 CD33, CD38 CD20, CD44 CD22, CD44 CD25, CD44 CD31, CD44 CD33, CD44 CD20, CD45 CD22, CD45 CD25, CD45 CD31, CD45 CD33, CD45 CD20, CD47 CD22, CD47 CD25, CD47 CD31, CD47 CD33, CD47 CD20, CD51 CD22, CD51 CD25, CD51 CD31, CD51 CD33, CD51 CD20, CD56 CD22, CD56 CD25, CD56 CD31, CD56 CD33, CD56 CD20, CD58 CD22, CD58 CD25, CD58 CD31, CD58 CD33, CD58 CD20, CD59 CD22, CD59 CD25, CD59 CD31, CD59 CD33, CD59 CD20, CD63 CD22, CD63 CD25, CD63 CD31, CD63 CD33, CD63 CD20, CD70 CD22, CD70 CD25, CD70 CD31, CD70 CD33, CD70 CD20, CD82 CD22, CD82 CD25, CD82 CD31, CD82 CD33, CD82 CD20, CD85D CD22, CD85D CD25, CD85D CD31, CD85D CD33, CD85D CD20, CD96 CD22, CD96 CD25, CD96 CD31, CD96 CD33, CD96 CD20, CD97 CD22, CD97 CD25, CD97 CD31, CD97 CD33, CD97 CD20, CD99 CD22, CD99 CD25, CD99 CD31, CD99 CD33, CD99 CD20, CD100 CD22, CD100 CD25, CD100 CD31, CD100 CD33, CD100 CD20, CD102 CD22, CD102 CD25, CD102 CD31, CD102 CD33, CD102 CD20, CD117 CD22, CD117 CD25, CD117 CD31, CD117 CD33, CD117 CD20, CD120B CD22, CD120B CD25, CD120B CD31, CD120B CD33, CD120B CD20, CD123 CD22, CD123 CD25, CD123 CD31, CD123 CD33, CD123 CD20, CD127 CD22, CD127 CD25, CD127 CD31, CD127 CD33, CD127 CD20, CD133 CD22, CD133 CD25, CD133 CD31, CD133 CD33, CD133 CD20, CD135 CD22, CD135 CD25, CD135 CD31, CD135 CD33, CD135 CD20, CD148 CD22, CD148 CD25, CD148 CD31, CD148 CD33, CD148 CD20, CD157 CD22, CD157 CD25, CD157 CD31, CD157 CD33, CD157 CD20, CD172b CD22, CD172b CD25, CD172b CD31, CD172b CD33, CD172b CD20, CD191 CD22, CD191 CD25, CD191 CD31, CD191 CD33, CD191 CD20, CD217 CD22, CD217 CD25, CD217 CD31, CD217 CD33, CD217 CD20, CD300a CD22, CD300a CD25, CD300a CD31, CD300a CD33, CD300a CD20, CD305 CD22, CD305 CD25, CD305 CD31, CD305 CD33, CD305 CD20, CD317 CD22, CD317 CD25, CD317 CD31, CD317 CD33, CD317 CD20, CD321 CD22, CD321 CD25, CD321 CD31, CD321 CD33, CD321 CD20, CLL1 CD22, CLL1 CD25, CLL1 CD31, CLL1 CD33, CLL1 CD20, FOLR2 CD22, FOLR2 CD25, FOLR2 CD31, FOLR2 CD33, FOLR2 CD20, NKG2D CD22, NKG2D CD25, NKG2D CD31, NKG2D CD33, NKG2D Ligand Ligand Ligand Ligand Ligand CD20, EMR2 CD22, EMR2 CD25, EMR2 CD31, EMR2 CD33, EMR2 CD34, CD7 CD37, CD7 CD38, CD7 CD44, CD7 CD45, CD7 CD34, CD11a CD37, CD11a CD38, CD11a CD44, CD11a CD45, CD11a CD34, CD15 CD37, CD15 CD38, CD15 CD44, CD15 CD45, CD15 CD34, CD18 CD37, CD18 CD38, CD18 CD44, CD18 CD45, CD18 CD34, CD19 CD37, CD19 CD38, CD19 CD44, CD19 CD45, CD19 CD34, CD20 CD37, CD20 CD38, CD20 CD44, CD20 CD45, CD20 CD34, CD22 CD37, CD22 CD38, CD22 CD44, CD22 CD45, CD22 CD34, CD25 CD37, CD25 CD38, CD25 CD44, CD25 CD45, CD25 CD34, CD31 CD37, CD31 CD38, CD31 CD44, CD31 CD45, CD31 CD34, CD33 CD37, CD33 CD38, CD33 CD44, CD33 CD45, CD33 — CD37, CD34 CD38, CD34 CD44, CD34 CD45, CD34 CD34, CD37 — CD38, CD37 CD44, CD37 CD45, CD37 CD34, CD38 CD37, CD38 — CD44, CD38 CD45, CD38 CD34, CD44 CD37, CD44 CD38, CD44 — CD45, CD44 CD34, CD45 CD37, CD45 CD38, CD45 CD44, CD45 — CD34, CD47 CD37, CD47 CD38, CD47 CD44, CD47 CD45, CD47 CD34, CD51 CD37, CD51 CD38, CD51 CD44, CD51 CD45, CD51 CD34, CD56 CD37, CD56 CD38, CD56 CD44, CD56 CD45, CD56 CD34, CD58 CD37, CD58 CD38, CD58 CD44, CD58 CD45, CD58 CD34, CD59 CD37, CD59 CD38, CD59 CD44, CD59 CD45, CD59 CD34, CD63 CD37, CD63 CD38, CD63 CD44, CD63 CD45, CD63 CD34, CD70 CD37, CD70 CD38, CD70 CD44, CD70 CD45, CD70 CD34, CD82 CD37, CD82 CD38, CD82 CD44, CD82 CD45, CD82 CD34, CD85D CD37, CD85D CD38, CD85D CD44, CD85D CD45, CD85D CD34, CD96 CD37, CD96 CD38, CD96 CD44, CD96 CD45, CD96 CD34, CD97 CD37, CD97 CD38, CD97 CD44, CD97 CD45, CD97 CD34, CD99 CD37, CD99 CD38, CD99 CD44, CD99 CD45, CD99 CD34, CD100 CD37, CD100 CD38, CD100 CD44, CD100 CD45, CD100 CD34, CD102 CD37, CD102 CD38, CD102 CD44, CD102 CD45, CD102 CD34, CD117 CD37, CD117 CD38, CD117 CD44, CD117 CD45, CD117 CD34, CD120B CD37, CD120B CD38, CD120B CD44, CD120B CD45, CD120B CD34, CD123 CD37, CD123 CD38, CD123 CD44, CD123 CD45, CD123 CD34, CD127 CD37, CD127 CD38, CD127 CD44, CD127 CD45, CD127 CD34, CD133 CD37, CD133 CD38, CD133 CD44, CD133 CD45, CD133 CD34, CD135 CD37, CD135 CD38, CD135 CD44, CD135 CD45, CD135 CD34, CD148 CD37, CD148 CD38, CD148 CD44, CD148 CD45, CD148 CD34, CD157 CD37, CD157 CD38, CD157 CD44, CD157 CD45, CD157 CD34, CD172b CD37, CD172b CD38, CD172b CD44, CD172b CD45, CD172b CD34, CD191 CD37, CD191 CD38, CD191 CD44, CD191 CD45, CD191 CD34, CD217 CD37, CD217 CD38, CD217 CD44, CD217 CD45, CD217 CD34, CD300a CD37, CD300a CD38, CD300a CD44, CD300a CD45, CD300a CD34, CD305 CD37, CD305 CD38, CD305 CD44, CD305 CD45, CD305 CD34, CD317 CD37, CD317 CD38, CD317 CD44, CD317 CD45, CD317 CD34, CD321 CD37, CD321 CD38, CD321 CD44, CD321 CD45, CD321 CD34, CLL1 CD37, CLL1 CD38, CLL1 CD44, CLL1 CD45, CLL1 CD34, FOLR2 CD37, FOLR2 CD38, FOLR2 CD44, FOLR2 CD45, FOLR2 CD34, NKG2D CD37, NKG2D CD38, NKG2D CD44, NKG2D CD45, NKG2D Ligand Ligand Ligand Ligand Ligand CD34, EMR2 CD37, EMR2 CD38, EMR2 CD44, EMR2 CD45, EMR2 CD47, CD7 CD51, CD7 CD56, CD7 CD58, CD7 CD59, CD7 CD47, CD11a CD51, CD11a CD56, CD11a CD58, CD11a CD59, CD11a CD47, CD15 CD51, CD15 CD56, CD15 CD58, CD15 CD59, CD15 CD47, CD18 CD51, CD18 CD56, CD18 CD58, CD18 CD59, CD18 CD47, CD19 CD51, CD19 CD56, CD19 CD58, CD19 CD59, CD19 CD47, CD20 CD51, CD20 CD56, CD20 CD58, CD20 CD59, CD20 CD47, CD22 CD51, CD22 CD56, CD22 CD58, CD22 CD59, CD22 CD47, CD25 CD51, CD25 CD56, CD25 CD58, CD25 CD59, CD25 CD47, CD31 CD51, CD31 CD56, CD31 CD58, CD31 CD59, CD31 CD47, CD33 CD51, CD33 CD56, CD33 CD58, CD33 CD59, CD33 CD47, CD34 CD51, CD34 CD56, CD34 CD58, CD34 CD59, CD34 CD47, CD37 CD51, CD37 CD56, CD37 CD58, CD37 CD59, CD37 CD47, CD38 CD51, CD38 CD56, CD38 CD58, CD38 CD59, CD38 CD47, CD44 CD51, CD44 CD56, CD44 CD58, CD44 CD59, CD44 CD47, CD45 CD51, CD45 CD56, CD45 CD58, CD45 CD59, CD45 — CD51, CD47 CD56, CD47 CD58, CD47 CD59, CD47 CD47, CD51 — CD56, CD51 CD58, CD51 CD59, CD51 CD47, CD56 CD51, CD56 — CD58, CD56 CD59, CD56 CD47, CD58 CD51, CD58 CD56, CD58 — CD59, CD58 CD47, CD59 CD51, CD59 CD56, CD59 CD58, CD59 — CD47, CD63 CD51, CD63 CD56, CD63 CD58, CD63 CD59, CD63 CD47, CD70 CD51, CD70 CD56, CD70 CD58, CD70 CD59, CD70 CD47, CD82 CD51, CD82 CD56, CD82 CD58, CD82 CD59, CD82 CD47, CD85D CD51, CD85D CD56, CD85D CD58, CD85D CD59, CD85D CD47, CD96 CD51, CD96 CD56, CD96 CD58, CD96 CD59, CD96 CD47, CD97 CD51, CD97 CD56, CD97 CD58, CD97 CD59, CD97 CD47, CD99 CD51, CD99 CD56, CD99 CD58, CD99 CD59, CD99 CD47, CD100 CD51, CD100 CD56, CD100 CD58, CD100 CD59, CD100 CD47, CD102 CD51, CD102 CD56, CD102 CD58, CD102 CD59, CD102 CD47, CD117 CD51, CD117 CD56, CD117 CD58, CD117 CD59, CD117 CD47, CD120B CD51, CD120B CD56, CD120B CD58, CD120B CD59, CD120B CD47, CD123 CD51, CD123 CD56, CD123 CD58, CD123 CD59, CD123 CD47, CD127 CD51, CD127 CD56, CD127 CD58, CD127 CD59, CD127 CD47, CD133 CD51, CD133 CD56, CD133 CD58, CD133 CD59, CD133 CD47, CD135 CD51, CD135 CD56, CD135 CD58, CD135 CD59, CD135 CD47, CD148 CD51, CD148 CD56, CD148 CD58, CD148 CD59, CD148 CD47, CD157 CD51, CD157 CD56, CD157 CD58, CD157 CD59, CD157 CD47, CD172b CD51, CD172b CD56, CD172b CD58, CD172b CD59, CD172b CD47, CD191 CD51, CD191 CD56, CD191 CD58, CD191 CD59, CD191 CD47, CD217 CD51, CD217 CD56, CD217 CD58, CD217 CD59, CD217 CD47, CD300a CD51, CD300a CD56, CD300a CD58, CD300a CD59, CD300a CD47, CD305 CD51, CD305 CD56, CD305 CD58, CD305 CD59, CD305 CD47, CD317 CD51, CD317 CD56, CD317 CD58, CD317 CD59, CD317 CD47, CD321 CD51, CD321 CD56, CD321 CD58, CD321 CD59, CD321 CD47, CLL1 CD51, CLL1 CD56, CLL1 CD58, CLL1 CD59, CLL1 CD47, FOLR2 CD51, FOLR2 CD56, FOLR2 CD58, FOLR2 CD59, FOLR2 CD47, NKG2D CD51, NKG2D CD56, NKG2D CD58, NKG2D CD59, NKG2D Ligand Ligand Ligand Ligand Ligand CD47, EMR2 CD51, EMR2 CD56, EMR2 CD58, EMR2 CD59, EMR2 CD63, CD7 CD70, CD7 CD82, CD7 CD85D, CD7 CD96, CD7 CD63, CD11a CD70, CD11a CD82, CD11a CD85D, CD11a CD96, CD11a CD63, CD15 CD70, CD15 CD82, CD15 CD85D, CD15 CD96, CD15 CD63, CD18 CD70, CD18 CD82, CD18 CD85D, CD18 CD96, CD18 CD63, CD19 CD70, CD19 CD82, CD19 CD85D, CD19 CD96, CD19 CD63, CD20 CD70, CD20 CD82, CD20 CD85D, CD20 CD96, CD20 CD63, CD22 CD70, CD22 CD82, CD22 CD85D, CD22 CD96, CD22 CD63, CD25 CD70, CD25 CD82, CD25 CD85D, CD25 CD96, CD25 CD63, CD31 CD70, CD31 CD82, CD31 CD85D, CD31 CD96, CD31 CD63, CD33 CD70, CD33 CD82, CD33 CD85D, CD33 CD96, CD33 CD63, CD34 CD70, CD34 CD82, CD34 CD85D, CD34 CD96, CD34 CD63, CD37 CD70, CD37 CD82, CD37 CD85D, CD37 CD96, CD37 CD63, CD38 CD70, CD38 CD82, CD38 CD85D, CD38 CD96, CD38 CD63, CD44 CD70, CD44 CD82, CD44 CD85D, CD44 CD96, CD44 CD63, CD45 CD70, CD45 CD82, CD45 CD85D, CD45 CD96, CD45 CD63, CD47 CD70, CD47 CD82, CD47 CD85D, CD47 CD96, CD47 CD63, CD51 CD70, CD51 CD82, CD51 CD85D, CD51 CD96, CD51 CD63, CD56 CD70, CD56 CD82, CD56 CD85D, CD56 CD96, CD56 CD63, CD58 CD70, CD58 CD82, CD58 CD85D, CD58 CD96, CD58 CD63, CD59 CD70, CD59 CD82, CD59 CD85D, CD59 CD96, CD59 — CD70, CD63 CD82, CD63 CD85D, CD63 CD96, CD63 CD63, CD70 — CD82, CD70 CD85D, CD70 CD96, CD70 CD63, CD82 CD70, CD82 — CD85D, CD82 CD96, CD82 CD63, CD85D CD70, CD85D CD82, CD85D — CD96, CD85D CD63, CD96 CD70, CD96 CD82, CD96 CD85D, CD96 — CD63, CD97 CD70, CD97 CD82, CD97 CD85D, CD97 CD96, CD97 CD63, CD99 CD70, CD99 CD82, CD99 CD85D, CD99 CD96, CD99 CD63, CD100 CD70, CD100 CD82, CD100 CD85D, CD100 CD96, CD100 CD63, CD102 CD70, CD102 CD82, CD102 CD85D, CD102 CD96, CD102 CD63, CD117 CD70, CD117 CD82, CD117 CD85D, CD117 CD96, CD117 CD63, CD120B CD70, CD120B CD82, CD120B CD85D, CD120B CD96, CD120B CD63, CD123 CD70, CD123 CD82, CD123 CD85D, CD123 CD96, CD123 CD63, CD127 CD70, CD127 CD82, CD127 CD85D, CD127 CD96, CD127 CD63, CD133 CD70, CD133 CD82, CD133 CD85D, CD133 CD96, CD133 CD63, CD135 CD70, CD135 CD82, CD135 CD85D, CD135 CD96, CD135 CD63, CD148 CD70, CD148 CD82, CD148 CD85D, CD148 CD96, CD148 CD63, CD157 CD70, CD157 CD82, CD157 CD85D, CD157 CD96, CD157 CD63, CD172b CD70, CD172b CD82, CD172b CD85D, CD172b CD96, CD172b CD63, CD191 CD70, CD191 CD82, CD191 CD85D, CD191 CD96, CD191 CD63, CD217 CD70, CD217 CD82, CD217 CD85D, CD217 CD96, CD217 CD63, CD300a CD70, CD300a CD82, CD300a CD85D, CD300a CD96, CD300a CD63, CD305 CD70, CD305 CD82, CD305 CD85D, CD305 CD96, CD305 CD63, CD317 CD70, CD317 CD82, CD317 CD85D, CD317 CD96, CD317 CD63, CD321 CD70, CD321 CD82, CD321 CD85D, CD321 CD96, CD321 CD63, CLL1 CD70, CLL1 CD82, CLL1 CD85D, CLL1 CD96, CLL1 CD63, FOLR2 CD70, FOLR2 CD82, FOLR2 CD85D, FOLR2 CD96, FOLR2 CD63, NKG2D CD70, NKG2D CD82, NKG2D CD85D, NKG2D CD96, NKG2D Ligand Ligand Ligand Ligand Ligand CD63, EMR2 CD70, EMR2 CD82, EMR2 CD85D, EMR2 CD96, EMR2 CD97, CD7 CD99, CD7 CD100, CD7 CD102, CD7 CD117, CD7 CD97, CD11a CD99, CD11a CD100, CD11a CD102, CD11a CD117, CD11a CD97, CD15 CD99, CD15 CD100, CD15 CD102, CD15 CD117, CD15 CD97, CD18 CD99, CD18 CD100, CD18 CD102, CD18 CD117, CD18 CD97, CD19 CD99, CD19 CD100, CD19 CD102, CD19 CD117, CD19 CD97, CD20 CD99, CD20 CD100, CD20 CD102, CD20 CD117, CD20 CD97, CD22 CD99, CD22 CD100, CD22 CD102, CD22 CD117, CD22 CD97, CD25 CD99, CD25 CD100, CD25 CD102, CD25 CD117, CD25 CD97, CD31 CD99, CD31 CD100, CD31 CD102, CD31 CD117, CD31 CD97, CD33 CD99, CD33 CD100, CD33 CD102, CD33 CD117, CD33 CD97, CD34 CD99, CD34 CD100, CD34 CD102, CD34 CD117, CD34 CD97, CD37 CD99, CD37 CD100, CD37 CD102, CD37 CD117, CD37 CD97, CD38 CD99, CD38 CD100, CD38 CD102, CD38 CD117, CD38 CD97, CD44 CD99, CD44 CD100, CD44 CD102, CD44 CD117, CD44 CD97, CD45 CD99, CD45 CD100, CD45 CD102, CD45 CD117, CD45 CD97, CD47 CD99, CD47 CD100, CD47 CD102, CD47 CD117, CD47 CD97, CD51 CD99, CD51 CD100, CD51 CD102, CD51 CD117, CD51 CD97, CD56 CD99, CD56 CD100, CD56 CD102, CD56 CD117, CD56 CD97, CD58 CD99, CD58 CD100, CD58 CD102, CD58 CD117, CD58 CD97, CD59 CD99, CD59 CD100, CD59 CD102, CD59 CD117, CD59 CD97, CD63 CD99, CD63 CD100, CD63 CD102, CD63 CD117, CD63 CD97, CD70 CD99, CD70 CD100, CD70 CD102, CD70 CD117, CD70 CD97, CD82 CD99, CD82 CD100, CD82 CD102, CD82 CD117, CD82 CD97, CD85D CD99, CD85D CD100, CD85D CD102, CD85D CD117, CD85D CD97, CD96 CD99, CD96 CD100, CD96 CD102, CD96 CD117, CD96 — CD99, CD97 CD100, CD97 CD102, CD97 CD117, CD97 CD97, CD99 — CD100, CD99 CD102, CD99 CD117, CD99 CD97, CD100 CD99, CD100 — CD102, CD100 CD117, CD100 CD97, CD102 CD99, CD102 CD100, CD102 — CD117, CD102 CD97, CD117 CD99, CD117 CD100, CD117 CD102, CD117 — CD97, CD120B CD99, CD120B CD100, CD120B CD102, CD120B CD117, CD120B CD97, CD123 CD99, CD123 CD100, CD123 CD102, CD123 CD117, CD123 CD97, CD127 CD99, CD127 CD100, CD127 CD102, CD127 CD117, CD127 CD97, CD133 CD99, CD133 CD100, CD133 CD102, CD133 CD117, CD133 CD97, CD135 CD99, CD135 CD100, CD135 CD102, CD135 CD117, CD135 CD97, CD148 CD99, CD148 CD100, CD148 CD102, CD148 CD117, CD148 CD97, CD157 CD99, CD157 CD100, CD157 CD102, CD157 CD117, CD157 CD97, CD172b CD99, CD172b CD100, CD172b CD102, CD172b CD117, CD172b CD97, CD191 CD99, CD191 CD100, CD191 CD102, CD191 CD117, CD191 CD97, CD217 CD99, CD217 CD100, CD217 CD102, CD217 CD117, CD217 CD97, CD300a CD99, CD300a CD100, CD300a CD102, CD300a CD117, CD300a CD97, CD305 CD99, CD305 CD100, CD305 CD102, CD305 CD117, CD305 CD97, CD317 CD99, CD317 CD100, CD317 CD102, CD317 CD117, CD317 CD97, CD321 CD99, CD321 CD100, CD321 CD102, CD321 CD117, CD321 CD97, CLL1 CD99, CLL1 CD100, CLL1 CD102, CLL1 CD117, CLL1 CD97, FOLR2 CD99, FOLR2 CD100, FOLR2 CD102, FOLR2 CD117, FOLR2 CD97, NKG2D CD99, NKG2D CD100, NKG2D CD102, NKG2D CD117, NKG2D Ligand Ligand Ligand Ligand Ligand CD97, EMR2 CD99, EMR2 CD100, EMR2 CD102, EMR2 CD117, EMR2 CD120B, CD7 CD123, CD7 CD127, CD7 CD133, CD7 CD135, CD7 CD120B, CD11a CD123, CD11a CD127, CD11a CD133, CD11a CD135, CD11a CD120B, CD15 CD123, CD15 CD127, CD15 CD133, CD15 CD135, CD15 CD120B, CD18 CD123, CD18 CD127, CD18 CD133, CD18 CD135, CD18 CD120B, CD19 CD123, CD19 CD127, CD19 CD133, CD19 CD135, CD19 CD120B, CD20 CD123, CD20 CD127, CD20 CD133, CD20 CD135, CD20 CD120B, CD22 CD123, CD22 CD127, CD22 CD133, CD22 CD135, CD22 CD120B, CD25 CD123, CD25 CD127, CD25 CD133, CD25 CD135, CD25 CD120B, CD31 CD123, CD31 CD127, CD31 CD133, CD31 CD135, CD31 CD120B, CD33 CD123, CD33 CD127, CD33 CD133, CD33 CD135, CD33 CD120B, CD34 CD123, CD34 CD127, CD34 CD133, CD34 CD135, CD34 CD120B, CD37 CD123, CD37 CD127, CD37 CD133, CD37 CD135, CD37 CD120B, CD38 CD123, CD38 CD127, CD38 CD133, CD38 CD135, CD38 CD120B, CD44 CD123, CD44 CD127, CD44 CD133, CD44 CD135, CD44 CD120B, CD45 CD123, CD45 CD127, CD45 CD133, CD45 CD135, CD45 CD120B, CD47 CD123, CD47 CD127, CD47 CD133, CD47 CD135, CD47 CD120B, CD51 CD123, CD51 CD127, CD51 CD133, CD51 CD135, CD51 CD120B, CD56 CD123, CD56 CD127, CD56 CD133, CD56 CD135, CD56 CD120B, CD58 CD123, CD58 CD127, CD58 CD133, CD58 CD135, CD58 CD120B, CD59 CD123, CD59 CD127, CD59 CD133, CD59 CD135, CD59 CD120B, CD63 CD123, CD63 CD127, CD63 CD133, CD63 CD135, CD63 CD120B, CD70 CD123, CD70 CD127, CD70 CD133, CD70 CD135, CD70 CD120B, CD82 CD123, CD82 CD127, CD82 CD133, CD82 CD135, CD82 CD120B, CD85D CD123, CD85D CD127, CD85D CD133, CD85D CD135, CD85D CD120B, CD96 CD123, CD96 CD127, CD96 CD133, CD96 CD135, CD96 CD120B, CD97 CD123, CD97 CD127, CD97 CD133, CD97 CD135, CD97 CD120B, CD99 CD123, CD99 CD127, CD99 CD133, CD99 CD135, CD99 CD120B, CD100 CD123, CD100 CD127, CD100 CD133, CD100 CD135, CD100 CD120B, CD102 CD123, CD102 CD127, CD102 CD133, CD102 CD135, CD102 CD120B, CD117 CD123, CD117 CD127, CD117 CD133, CD117 CD135, CD117 — CD123, CD120B CD127, CD120B CD133, CD120B CD135, CD120B CD120B, CD123 — CD127, CD123 CD133, CD123 CD135, CD123 CD120B, CD127 CD123, CD127 — CD133, CD127 CD135, CD127 CD120B, CD133 CD123, CD133 CD127, CD133 — CD135, CD133 CD120B, CD135 CD123, CD135 CD127, CD135 CD133, CD135 — CD120B, CD148 CD123, CD148 CD127, CD148 CD133, CD148 CD135, CD148 CD120B, CD157 CD123, CD157 CD127, CD157 CD133, CD157 CD135, CD157 CD120B, CD172b CD123, CD172b CD127, CD172b CD133, CD172b CD135, CD172b CD120B, CD191 CD123, CD191 CD127, CD191 CD133, CD191 CD135, CD191 CD120B, CD217 CD123, CD217 CD127, CD217 CD133, CD217 CD135, CD217 CD120B, CD300a CD123, CD300a CD127, CD300a CD133, CD300a CD135, CD300a CD120B, CD305 CD123, CD305 CD127, CD305 CD133, CD305 CD135, CD305 CD120B, CD317 CD123, CD317 CD127, CD317 CD133, CD317 CD135, CD317 CD120B, CD321 CD123, CD321 CD127, CD321 CD133, CD321 CD135, CD321 CD120B, CLL1 CD123, CLL1 CD127, CLL1 CD133, CLL1 CD135, CLL1 CD120B, FOLR2 CD123, FOLR2 CD127, FOLR2 CD133, FOLR2 CD135, FOLR2 CD120B, NKG2D CD123, NKG2D CD127, NKG2D CD133, NKG2D CD135, NKG2D Ligand Ligand Ligand Ligand Ligand CD120B, EMR2 CD123, EMR2 CD127, EMR2 CD133, EMR2 CD135, EMR2 CD148, CD7 CD157, CD7 CD172b, CD7 CD191, CD7 CD217, CD7 CD148, CD11a CD157, CD11a CD172b, CD11a CD191, CD11a CD217, CD11a CD148, CD15 CD157, CD15 CD172b, CD15 CD191, CD15 CD217, CD15 CD148, CD18 CD157, CD18 CD172b, CD18 CD191, CD18 CD217, CD18 CD148, CD19 CD157, CD19 CD172b, CD19 CD191, CD19 CD217, CD19 CD148, CD20 CD157, CD20 CD172b, CD20 CD191, CD20 CD217, CD20 CD148, CD22 CD157, CD22 CD172b, CD22 CD191, CD22 CD217, CD22 CD148, CD25 CD157, CD25 CD172b, CD25 CD191, CD25 CD217, CD25 CD148, CD31 CD157, CD31 CD172b, CD31 CD191, CD31 CD217, CD31 CD148, CD33 CD157, CD33 CD172b, CD33 CD191, CD33 CD217, CD33 CD148, CD34 CD157, CD34 CD172b, CD34 CD191, CD34 CD217, CD34 CD148, CD37 CD157, CD37 CD172b, CD37 CD191, CD37 CD217, CD37 CD148, CD38 CD157, CD38 CD172b, CD38 CD191, CD38 CD217, CD38 CD148, CD44 CD157, CD44 CD172b, CD44 CD191, CD44 CD217, CD44 CD148, CD45 CD157, CD45 CD172b, CD45 CD191, CD45 CD217, CD45 CD148, CD47 CD157, CD47 CD172b, CD47 CD191, CD47 CD217, CD47 CD148, CD51 CD157, CD51 CD172b, CD51 CD191, CD51 CD217, CD51 CD148, CD56 CD157, CD56 CD172b, CD56 CD191, CD56 CD217, CD56 CD148, CD58 CD157, CD58 CD172b, CD58 CD191, CD58 CD217, CD58 CD148, CD59 CD157, CD59 CD172b, CD59 CD191, CD59 CD217, CD59 CD148, CD63 CD157, CD63 CD172b, CD63 CD191, CD63 CD217, CD63 CD148, CD70 CD157, CD70 CD172b, CD70 CD191, CD70 CD217, CD70 CD148, CD82 CD157, CD82 CD172b, CD82 CD191, CD82 CD217, CD82 CD148, CD85D CD157, CD85D CD172b, CD85D CD191, CD85D CD217, CD85D CD148, CD96 CD157, CD96 CD172b, CD96 CD191, CD96 CD217, CD96 CD148, CD97 CD157, CD97 CD172b, CD97 CD191, CD97 CD217, CD97 CD148, CD99 CD157, CD99 CD172b, CD99 CD191, CD99 CD217, CD99 CD148, CD100 CD157, CD100 CD172b, CD100 CD191, CD100 CD217, CD100 CD148, CD102 CD157, CD102 CD172b, CD102 CD191, CD102 CD217, CD102 CD148, CD117 CD157, CD117 CD172b, CD117 CD191, CD117 CD217, CD117 CD148, CD120B CD157, CD120B CD172b, CD120B CD191, CD120B CD217, CD120B CD148, CD123 CD157, CD123 CD172b, CD123 CD191, CD123 CD217, CD123 CD148, CD127 CD157, CD127 CD172b, CD127 CD191, CD127 CD217, CD127 CD148, CD133 CD157, CD133 CD172b, CD133 CD191, CD133 CD217, CD133 CD148, CD135 CD157, CD135 CD172b, CD135 CD191, CD135 CD217, CD135 — CD157, CD148 CD172b, CD148 CD191, CD148 CD217, CD148 CD148, CD157 — CD172b, CD157 CD191, CD157 CD217, CD157 CD148, CD172b CD157, CD172b — CD191, CD172b CD217, CD172b CD148, CD191 CD157, CD191 CD172b, CD191 — CD217, CD191 CD148, CD217 CD157, CD217 CD172b, CD217 CD191, CD217 — CD148, CD300a CD157, CD300a CD172b, CD300a CD191, CD300a CD217, CD300a CD148, CD305 CD157, CD305 CD172b, CD305 CD191, CD305 CD217, CD305 CD148, CD317 CD157, CD317 CD172b, CD317 CD191, CD317 CD217, CD317 CD148, CD321 CD157, CD321 CD172b, CD321 CD191, CD321 CD217, CD321 CD148, CLL1 CD157, CLL1 CD172b, CLL1 CD191, CLL1 CD217, CLL1 CD148, FOLR2 CD157, FOLR2 CD172b, FOLR2 CD191, FOLR2 CD217, FOLR2 CD148, NKG2D CD157, NKG2D CD172b, NKG2D CD191, NKG2D CD217, NKG2D Ligand Ligand Ligand Ligand Ligand CD148, EMR2 CD157, EMR2 CD172b, EMR2 CD191, EMR2 CD217, EMR2

(i) Mutated Lineage-Specific Cell-Surface Antigens

In some embodiments, the hematopoietic cells (HSCs) described herein may contain an edited gene encoding one or more lineage-specific cell-surface proteins of interest in mutated form (mutants or variants, which are used herein interchangeably), which has reduced binding or no binding to a cytotoxic agent as described herein. The variants may lack the epitope to which the cytotoxic agent binds. Alternatively, the mutants may carry one or more mutations of the epitope to which the cytotoxic agent binds, such that binding to the cytotoxic agent is reduced or abolished as compared to the natural or wild-type lineage-specific cell-surface protein counterpart. Such a variant is preferred to maintain substantially similar biological activity as the wild-type counterpart.

As used herein, the term “reduced binding” refers to binding that is reduced by at least 25%. The level of binding may refer to the amount of binding of the cytotoxic agent to a hematopoietic cell or descendant thereof or the amount of binding of the cytotoxic agent to the lineage-specific cell-surface protein. The level of binding of a hematopoietic cell or descendant thereof that has been manipulated to a cytotoxic agent may be relative to the level of binding of the cytotoxic agent to a hematopoietic cell or descendant thereof that has not been manipulated as determined by the same assay under the same conditions. Alternatively, the level of binding of a lineage-specific cell-surface protein that lacks an epitope to a cytotoxic agent may be relative to the level of binding of the cytotoxic agent to a lineage-specific cell-surface protein that contains the epitope (e.g., a wild-type protein) as determined by the same assay under the same conditions. In some embodiments, the binding is reduced by at least 25%, 30%, 40%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%. In some embodiments, the binding is reduced such that there is substantially no detectable binding in a conventional assay.

As used herein, “no binding” refers to substantially no binding, e.g., no detectable binding or only baseline binding as determined in a conventional binding assay. In some embodiments, there is no binding between the hematopoietic cells or descendants thereof that have been manipulated and the cytotoxic agent. In some embodiments, there is no detectable binding between the hematopoietic cells or descendants thereof that have been manipulated and the cytotoxic agent. In some embodiments, no binding of the hematopoietic cells or descendant thereof to the cytotoxic agent refers to a baseline level of binding, as shown using any conventional binding assay known in the art. In some embodiments, the level of binding of the hematopoietic cells or descendants thereof that have been manipulated and the cytotoxic agent is not biologically significant. The term “no binding” is not intended to require the absolute absence of binding.

A cell that is “negative” for a given lineage-specific cell-surface antigen has a substantially reduced expression level of the lineage-specific antigen as compared with its naturally-occurring counterpart (e.g., otherwise similar, unmodified cells), e.g., not detectable or not distinguishable from background levels, e.g., using a flow cytometry assay, e.g., an assay of Example 1. In some instances, a cell that is negative for the lineage-specific cell-surface antigen has a level of less than 10%, 5%, 2%, or 1% of as compared with its naturally-occurring counterpart. The variant may share a sequence homology of at least 80% (e.g., 85%, 90%, 95%, 97%, 98%, 99%, or above) as the wild-type counterpart and, in some embodiments, may contain no other mutations in addition to those for mutating or deleting the epitope of interest. The “percent identity” of two amino acid sequences is determined using the algorithm of Karlin and Altschul Proc. Natl. Acad. Sci. USA 87:2264-68, 1990, modified as in Karlin and Altschul Proc. Natl. Acad Sci. USA 90:5873-77, 1993. Such an algorithm is incorporated into the NBLAST and XBLAST programs (version 2.0) of Altschul, et al. J. Mol. Biol. 215:403-10, 1990. BLAST protein searches can be performed with the XBLAST program, score=50, wordlength=3 to obtain amino acid sequences homologous to the protein molecules of the invention. Where gaps exist between two sequences, Gapped BLAST can be utilized as described in Altschul et al., Nucleic Acids Res. 25(17):3389-3402, 1997. When utilizing BLAST and Gapped BLAST programs, the default parameters of the respective programs (e.g., XBLAST and NBLAST) can be used.

In some instances, the variant contains one or more amino acid residue substitutions (e.g., 2, 3, 4, 5, or more) within the epitope of interest such that the cytotoxic agent does not bind or has reduced binding to the mutated epitope. Such a variant may have substantially reduced binding affinity to the cytotoxic agent (e.g., having a binding affinity that is at least 40%, 50%, 60%, 70%, 80% or 90% lower than its wild-type counterpart). In some examples, such a variant may have abolished binding activity to the cytotoxic agent. In other instances, the variant contains a deletion of a region that comprises the epitope of interest. Such a region may be encoded by an exon. In some embodiments, the region is a domain of the lineage-specific cell-surface protein of interest that encodes the epitope. In one example, the variant has just the epitope deleted. The length of the deleted region may range from 3-60 amino acids, e.g., 5-50, 5-40, 10-30, 10-20, etc.

The mutation(s) or deletions in a mutant of a lineage-specific cell-surface antigen may be within or surround a non-essential epitope such that the mutation(s) or deletion(s) do not substantially affect the bioactivity of the protein.

As used herein, the term “epitope” refers to an amino acid sequence (linear or conformational) of a protein, such as a lineage-specific cell-surface antigens, that is bound by the CDRs of an antibody. In some embodiments, the cytotoxic agent binds to one or more (e.g., at least 2, 3, 4, 5 or more) epitopes of a lineage-specific cell-surface antigens. In some embodiments, the cytotoxic agent binds to more than one epitope of the lineage-specific cell-surface antigen and the hematopoietic cells are manipulated such that each of the epitopes is absent and/or unavailable for binding by the cytotoxic agent.

In some embodiments, the genetically engineered HSCs described herein have one or more edited genes of lineage-specific cell-surface antigens such that the edited genes express mutated lineage-specific cell-surface antigens with mutations in one or more non-essential epitopes. A non-essential epitope (or a fragment comprising such) refers to a domain within the lineage-specific protein, the mutation in which (e.g., deletion) is less likely to substantially affect the bioactivity of the lineage-specific protein and thus the bioactivity of the cells expressing such. For example, when hematopoietic cells comprising a deletion or mutation of a non-essential epitope of a lineage-specific cell-surface antigen, such hematopoietic cells are able to proliferate and/or undergo erythropoietic differentiation to a similar level as hematopoietic cells that express a wild-type lineage-specific cell-surface antigen.

Non-essential epitopes of a lineage-specific cell-surface antigen can be identified by the methods described herein or by conventional methods relating to protein structure-function prediction. For example, a non-essential epitope of a protein can be predicted based on comparing the amino acid sequence of a protein from one species with the sequence of the protein from other species. Non-conserved domains are usually not essential to the functionality of the protein. As will be evident to one of ordinary skill in the art, non-essential epitope of a protein is predicted using an algorithm or software, such as the PROVEAN software (see, e.g., see: provean.jcvi.org; Choi et al. PLoS ONE (2012) 7(10): e46688), to predict potential non-essential epitopes in a lineage-specific protein of interest (“candidate non-essential epitope”). Mutations, including substitution and/or deletion, many be made in any one or more amino acid residues of a candidate non-essential epitope using convention nucleic acid modification technologies. The protein variants thus prepared may be introduced into a suitable type of cells, such as hematopoietic cells, and the functionality of the protein variant can be investigated to confirm that the candidate non-essential epitope is indeed a non-essential epitope.

Alternatively, a non-essential epitope of a lineage-specific cell-surface antigen may be identified by introducing a mutation into a candidate region in a lineage-specific protein of interest in a suitable type of host cells (e.g., hematopoietic cells) and examining the functionality of the mutated lineage-specific protein in the host cells. If the mutated lineage-specific protein maintains substantially the biological activity of the native counterpart, this indicates that the region where the mutation is introduced is non-essential to the function of the lineage-specific protein.

Methods for assessing the functionality of the lineage-specific cell-surface antigen and the hematopoietic cells or descendants thereof will be known in the art and include, for example, proliferation assays, differentiation assays, colony formation, expression analysis (e.g., gene and/or protein), protein localization, intracellular signaling, functional assays, and in vivo humanized mouse models.

Any of the methods for identifying and/or verifying non-essential epitopes in lineage-specific cell-surface antigens is also within the scope of the present disclosure.

(ii) Hematopoietic Stem Cells

In some embodiments, the hematopoietic cells described herein are hematopoietic stem cells. Hematopoietic stem cells (HSCs) are capable of giving rise to both myeloid and lymphoid progenitor cells that further give rise to myeloid cells (e.g., monocytes, macrophages, neutrophils, basophils, dendritic cells, erythrocytes, platelets, etc) and lymphoid cells (e.g., T cells, B cells, NK cells), respectively. HSCs are characterized by the expression of the cell surface marker CD34 (e.g., CD34⁺), which can be used for the identification and/or isolation of HSCs, and absence of cell surface markers associated with commitment to a cell lineage.

In some embodiments, the HSCs are obtained from a subject, such as a mammalian subject. In some embodiments, the mammalian subject is a non-human primate, a rodent (e.g., mouse or rat), a bovine, a porcine, an equine, or a domestic animal. In some embodiments, the HSCs are obtained from a human patient, such as a human patient having a hematopoietic malignancy. In some embodiments, the HSCs are obtained from a healthy donor. In some embodiments, the HSCs are obtained from the subject to whom the immune cells expressing the chimeric receptors will be subsequently administered. HSCs that are administered to the same subject from which the cells were obtained are referred to as autologous cells, whereas HSCs that are obtained from a subject who is not the subject to whom the cells will be administered are referred to as allogeneic cells.

In some embodiments, the HSCs that are administered to the subject are allogeneic cells. In some embodiments, the HSCs are obtained from a donor having a HLA haplotype that is matched with the HLA haplotype of the subject. Human Leukocyte Antigen (HLA) encodes major histocompatibility complex (MHC) proteins in humans. MHC molecules are present on the surface of antigen-presenting cells as well as many other cell types and present peptides of self and non-self (e.g., foreign) antigens for immunosurveillance. However, HLA are highly polymorphic, which results in many distinct alleles. Different (foreign, non-self) alleles may be antigenic and stimulate robust adverse immune responses, particularly in organ and cell transplantation. HLA molecules that are recognized as foreign (non-self) can result in transplant rejection. In some embodiments, it is desirable to administer HSCs from donor that has the same HLA type as the patient to reduce the incidence of rejection.

The HLA loci of a donor subject may be typed to identify an individual as a HLA-matched donor for the subject. Methods for typing the HLA loci will be evident to one of ordinary skill in the art and include, for example, serology (serotyping), cellular typing, gene sequencing, phenotyping, and PCR methods. A HLA from a donor is considered “matched” with the HLA of the subject if the HLA loci of the donor and the subject are identical or sufficiently similar such that an adverse immune response is not expected.

In some embodiments, the HLA from the donor is not matched with the HLA of the subject. In some embodiments, the subject is administered HSCs that are not HLA matched with the HLA of the subject. In some embodiments, the subject is further administered one or more immunosuppressive agents to reduce or prevent rejection of the donor HSC cells. In some embodiments, the HSCs do not comprise a CART.

HSCs may be obtained from any suitable source using convention means known in the art. In some embodiments, HSCs are obtained from a sample from a subject (or donor), such as bone marrow sample or from a blood sample. Alternatively or in addition, HSCs may be obtained from an umbilical cord. In some embodiments, the HSCs are from bone marrow, cord blood cells, or peripheral blood mononuclear cells (PBMCs). In general, bone marrow cells may be obtained from iliac crest, femora, tibiae, spine, rib or other medullary spaces of a subject (or donor). Bone marrow may be taken out of the patient and isolated through various separations and washing procedures known in the art. An exemplary procedure for isolation of bone marrow cells comprises the following steps: a) extraction of a bone marrow sample; b) centrifugal separation of bone marrow suspension in three fractions and collecting the intermediate fraction, or buffycoat; c) the buffycoat fraction from step (b) is centrifuged one more time in a separation fluid, commonly Ficoll™, and an intermediate fraction which contains the bone marrow cells is collected: and d) washing of the collected fraction from step (c) for recovery of re-transfusable bone marrow cells.

HSCs typically reside in the bone marrow but can be mobilized into the circulating blood by administering a mobilizing agent in order to harvest HSCs from the peripheral blood. In some embodiments, the subject (or donor) from which the HSCs are obtained is administered a mobilizing agent, such as granulocyte colony-stimulating factor (G-CSF). The number of the HSCs collected following mobilization using a mobilizing agent is typically greater than the number of cells obtained without use of a mobilizing agent.

The HSCs for use in the methods described herein may express the lineage-specific cell-surface antigen of interest. Upon any of the modifications described herein (e.g., genetic modification or incubation with a blocking agent), the HSCs would not be targeted by the cytotoxicity agent also described herein. Alternatively, the HSCs for use in the methods described herein may not express the lineage-specific cell surface protein of interest (e.g., CD19); however, descendant cells differentiated from the HSCs (e.g., B cells) express the lineage-specific cell surface protein. Upon genetic modification, an endogenous gene of the HSCs coding for the lineage-specific cell surface protein may be disrupted at a region encoding a non-essential epitope of the lineage-specific cell surface protein. Descendant cells differentiated from such modified HSCs (e.g., in vivo) would express a modified lineage-specific cell surface protein having the non-essential epitope mutated such that they would not be targeted by the cytotoxicity agent capable of binding the non-essential epitope.

In some embodiments, a sample is obtained from a subject (or donor) and is then enriched for a desired cell type (e.g. CD34⁺/CD33⁻ cells). For example, PBMCs and/or CD34⁺ hematopoietic cells can be isolated from blood as described herein. Cells can also be isolated from other cells, for example by isolation and/or activation with an antibody binding to an epitope on the cell surface of the desired cell type. Another method that can be used includes negative selection using antibodies to cell surface markers to selectively enrich for a specific cell type without activating the cell by receptor engagement.

Populations of HSC can be expanded prior to or after manipulating the HSC such that they don't bind the cytotoxic agent or have reduced binding to the cytotoxic agent. The cells may be cultured under conditions that comprise an expansion medium comprising one or more cytokines, such as stem cell factor (SCF), Flt-3 ligand (Flt3L), thrombopoietin (TPO), Interleukin 3 (IL-3), or Interleukin 6 (IL-6). The cell may be expanded for about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 days or any range necessary. In some embodiments, the HSC are expanded after isolation of a desired cell population (e.g., CD34⁺/CD33⁻) from a sample obtained from a subject (or donor) and prior to manipulation (e.g., genetic engineering, contact with a blocking agent). In some embodiments, the HSC are expanded after genetic engineering, thereby selectively expanding cells that have undergone the genetic modification and lack the epitope (e.g., have a deletion or substitution of at least a portion of the epitope) of the lineage-specific cell-surface antigen to which the cytotoxic agent binds. In some embodiments, a cell (“a clone”) or several cells having a desired characteristic (e.g., phenotype or genotype) following genetic modification may be selected and independently expanded. In some embodiments, the HSC are expanded prior to contacting the HSC with a blocking agent that binds the epitope of the lineage-specific cell-surface antigens, thereby providing a population of HSC expressing the lineage-specific cell-surface antigens that cannot be bound by the cytotoxic agent due to blocking of the corresponding epitope by the blocking agent.

(iii) Preparation of Genetically Engineered Hematopoietic Cells

Any of the genetically engineering hematopoietic cells, such as HSCs, that carry edited genes of one or more lineage-specific cell-surface antigens can be prepared by a routine method or by a method described herein. In some embodiments, the genetic engineering is performed using genome editing. As used herein, “genome editing” refers to a method of modifying the genome, including any protein-coding or non-coding nucleotide sequence, of an organism to knock out the expression of a target gene. In general, genome editing methods involve use of an endonuclease that is capable of cleaving the nucleic acid of the genome, for example at a targeted nucleotide sequence. Repair of the double-stranded breaks in the genome may be repaired introducing mutations and/or exogenous nucleic acid may be inserted into the targeted site.

Genome editing methods are generally classified based on the type of endonuclease that is involved in generating double stranded breaks in the target nucleic acid. These methods include use of zinc finger nucleases (ZFN), transcription activator-like effector-based nuclease (TALEN), meganucleases, and CRISPR/Cas systems.

In some embodiments, the modified cells are manipulated as described herein using the TALEN technology known in the art. In general, TALENs are engineered restriction enzymes that can specifically bind and cleave a desired target DNA molecule. A TALEN typically contains a Transcriptional Activator-Like Effector (TALE) DNA-binding domain fused to a DNA cleavage domain. The DNA binding domain may contain a highly conserved 33-34 amino acid sequence with a divergent 2 amino acid RVD (repeat variable dipeptide motif) at positions 12 and 13. The RVD motif determines binding specificity to a nucleic acid sequence and can be engineered according to methods known to those of skill in the art to specifically bind a desired DNA sequence. In one example, the DNA cleavage domain may be derived from the FokI endonuclease. The FokI domain functions as a dimer, requiring two constructs with unique DNA binding domains for sites in the target genome with proper orientation and spacing. TALENs specific to sequences in a target gene of interest (e.g., CD19, CD33) can be constructed using any method known in the art.

A TALEN specific to a target gene of interest can be used inside a cell to produce a double-stranded break (DSB). A mutation can be introduced at the break site if the repair mechanisms improperly repair the break via non-homologous end joining. For example, improper repair may introduce a frame shift mutation. Alternatively, a foreign DNA molecule having a desired sequence can be introduced into the cell along with the TALEN. Depending on the sequence of the foreign DNA and chromosomal sequence, this process can be used to correct a defect or introduce a DNA fragment into a target gene of interest, or introduce such a defect into the endogenous gene, thus decreasing expression of the target gene.

In some embodiments, one or more population of hematopoietic cells is generated by genetic engineering of a lineage-specific cell-surface antigen (e.g., those described herein) using a TALEN. The genetically engineered hematopoietic cells may not express the lineage-specific cell-surface antigen. Alternatively, the hematopoietic cells may be engineered to express an altered version of the lineage-specific cell-surface antigen, e.g., having a deletion or mutation relative to the wild-type counterpart. Such a mutated lineage-specific cell-surface antigen may preserve a certain level of the bioactivity as the wild-type counterpart. In some embodiments, a population of hematopoietic cells containing a mutated CD33 is generated by genetic engineering using a TALEN. In some embodiments, exon 2 or exon 3 of CD33 is mutated using a TALEN. In some examples, a population of hematopoietic cells containing a mutated CD19 is generated by genetic engineering using a TALEN. In some embodiments, exon 2 or exon 4 of CD19 is mutated using a TALEN.

In some embodiments, the cells can be genetically manipulated using zinc finger (ZFN) technology known in the art. In general, zinc finger mediated genomic editing involves use of a zinc finger nuclease, which typically comprises a DNA binding domain (i.e., zinc finger) and a cleavage domain (i.e., nuclease). The zinc finger binding domain may be engineered to recognize and bind to any target gene of interest (e.g., CD19, CD33) using methods known in the art and in particular, may be designed to recognize a DNA sequence ranging from about 3 nucleotides to about 21 nucleotides in length, or from about 8 to about 19 nucleotides in length. Zinc finger binding domains typically comprise at least three zinc finger recognition regions (e.g., zinc fingers).

Restriction endonucleases (restriction enzymes) capable of sequence-specific binding to DNA (at a recognition site) and cleaving DNA at or near the site of binding are known in the art and may be used to form ZFN for use in genomic editing. For example, Type IIS restriction endonucleases cleave DNA at sites removed from the recognition site and have separable binding and cleavage domains. In one example, the DNA cleavage domain may be derived from the FokI endonuclease.

In some embodiments, one or more population of hematopoietic cells is generated by genetic engineering of a lineage-specific cell-surface antigen (e.g., those described herein) using a ZFN. The genetically engineered hematopoietic cells may not express the lineage-specific cell-surface antigen. Alternatively, the hematopoietic cells may be engineered to express an altered version of the lineage-specific cell-surface antigen, e.g., having a deletion or mutation relative to the wild-type counterpart. Such a mutated lineage-specific cell-surface antigen may preserve a certain level of the bioactivity as the wild-type counterpart. In some examples, a population of hematopoietic cells containing a mutated CD33 is generated by genetic engineering using a ZFN. In some embodiments, exon 2 or exon 3 of CD33 is mutated using a ZFN. In some examples, a population of hematopoietic cells containing a mutated CD19 is generated by genetic engineering using a ZFN. In some embodiments, exon 2 or exon 4 of CD19 is mutated using a ZFN.

In one aspect of the present disclosure, the replacement of cancer cells by a modified population of normal cells is performed using normal cells that have been manipulated such that the cells do not bind the cytotoxic agent. Such modification may include the deletion or mutation of an epitope of the lineage specific protein using a CRISPR-Cas system, where the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas system is an engineered, non-naturally occurring CRISPR-Cas system.

The present disclosure utilizes the CRISPR/Cas system that hybridizes with a target sequence in a lineage specific protein polynucleotide, where the CRISPR/Cas system comprises a Cas endonuclease and an engineered crRNA/tracrRNA (or single guide RNA). In some embodiments, the CRISPR/Cas system includes a crRNA and does not include a tracrRNA sequence. CRISPR/Cas complex can bind to the lineage specific protein polynucleotide and allow the cleavage of the protein polynucleotide, thereby modifying the polynucleotide.

The CRISPR/Cas system of the present disclosure may bind to and/or cleave the region of interest within a cell-surface lineage-specific protein in a coding or non-coding region, within or adjacent to the gene, such as, for example, a leader sequence, trailer sequence or intron, or within a non-transcribed region, either upstream or downstream of the coding region. The guide RNAs (gRNAs) used in the present disclosure may be designed such that the gRNA directs binding of the Cas enzyme-gRNA complexes to a pre-determined cleavage sites (target site) in a genome. The cleavage sites may be chosen so as to release a fragment that contains a region of unknown sequence, or a region containing a SNP, nucleotide insertion, nucleotide deletion, rearrangement, etc.

Cleavage of a gene region may comprise cleaving one or two strands at the location of the target sequence by the Cas enzyme. In one embodiment, such, cleavage can result in decreased transcription of a target gene. In another embodiment, the cleavage can further comprise repairing the cleaved target polynucleotide by homologous recombination with an exogenous template polynucleotide, wherein the repair results in an insertion, deletion, or substitution of one or more nucleotides of the target polynucleotide.

The terms “gRNA.” “guide RNA” and “CRISPR guide sequence” may be used interchangeably throughout and refer to a nucleic acid comprising a sequence that determines the specificity of a Cas DNA binding protein of a CRISPR/Cas system. A gRNA hybridizes to (complementary to, partially or completely) a target nucleic acid sequence in the genome of a host cell. The gRNA or portion thereof that hybridizes to the target nucleic acid may be between 15-25 nucleotides, 18-22 nucleotides, or 19-21 nucleotides in length. In some embodiments, the gRNA sequence that hybridizes to the target nucleic acid is 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 nucleotides in length. In some embodiments, the gRNA sequence that hybridizes to the target nucleic acid is between 10-30, or between 15-25, nucleotides in length.

In addition to a sequence that binds to a target nucleic acid, in some embodiments, the gRNA also comprises a scaffold sequence. Expression of a gRNA encoding both a sequence complementary to a target nucleic acid and scaffold sequence has the dual function of both binding (hybridizing) to the target nucleic acid and recruiting the endonuclease to the target nucleic acid, which may result in site-specific CRISPR activity. In some embodiments, such a chimeric gRNA may be referred to as a single guide RNA (sgRNA).

As used herein, a “scaffold sequence,” also referred to as a tracrRNA, refers to a nucleic acid sequence that recruits a Cas endonuclease to a target nucleic acid bound (hybridized) to a complementary gRNA sequence. Any scaffold sequence that comprises at least one stem loop structure and recruits an endonuclease may be used in the genetic elements and vectors described herein. Exemplary scaffold sequences will be evident to one of skill in the art and can be found, for example, in Jinek, et al. Science (2012) 337(6096):816-821. Ran, et al. Nature Protocols (2013) 8:2281-2308. PCT Application No. WO2014/093694, and PCT Application No. WO2013/176772. In some embodiments, the CRISPR-Cas system does not include a tracrRNA sequence.

In some embodiments, the gRNA sequence does not comprise a scaffold sequence and a scaffold sequence is expressed as a separate transcript. In such embodiments, the gRNA sequence further comprises an additional sequence that is complementary to a portion of the scaffold sequence and functions to bind (hybridize) the scaffold sequence and recruit the endonuclease to the target nucleic acid.

In some embodiments, the gRNA sequence is at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 966, 97%, 98%, 99%, or at least 100% complementary to a target nucleic acid (see also U.S. Pat. No. 8,697,359, which is incorporated by reference for its teaching of complementarity of a gRNA sequence with a target polynucleotide sequence). It has been demonstrated that mismatches between a CRISPR guide sequence and the target nucleic acid near the 3′ end of the target nucleic acid may abolish nuclease cleavage activity (Upadhyay, et al. Genes Genome Genetics (2013) 3(12):2233-2238). In some embodiments, the gRNA sequence is at least 50% 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or at least 100% complementary to the 3′ end of the target nucleic acid (e.g., the last 5, 6, 7, 8, 9, or 10 nucleotides of the 3′ end of the target nucleic acid).

Example sgRNA sequences targeting intron 1, intron 2 or intron 4 of CD19 are provided in Table 3. Example sgRNA sequence targeting introns 1 and 2 of CD33 are provided in Table 4. Additional guide RNAs for editing CD19 and CD33 are provide below. As will be evident to one of ordinary skill in the art, selection of sgRNA sequences may depend on factors such as the number of predicted on-target and/or off-target binding sites. In some embodiments, the sgRNA sequence is selected to maximize potential on-target and minimize potential off-target sites.

As would be evident to one of ordinary skill in the art, various tools may be used to design and/or optimize the sequence of a sgRNA, for example to increase the specificity and/or precision of genomic editing. In general, candidate sgRNAs may be designed by identifying a sequence within the target region that has a high predicted On-target efficiency and low Off-target efficiency based on any of the available web-based tools. Candidate sgRNAs may be further assessed by manual inspection and/or experimental screening. Examples of web-based tools include, without limitation, CRISPR seek, CRISPR Design Tool, Cas-OFFinder, E-CRISP, ChopChop, CasOT, CRISPR direct, CRISPOR, BREAKING-CAS, CrispRGold, and CCTop. See, e.g., Safari, et al. Current Pharma. Biotechol. (2017) 18(13).

In some embodiments, the Cas endonuclease is a Cas9 nuclease (or variant thereof) or a Cpf1 nuclease (or variant thereof). Cas9 endonucleases cleave double stranded DNA of a target nucleic acid resulting in blunt ends, whereas cleavage with Cpf1 nucleases results in staggered ends of the nucleic acid.

In general, the target nucleic acid is flanked on the 3′ side or 5′ side by a protospacer adjacent motif (PAM) that may interact with the endonuclease and be further involved in targeting the endonuclease activity to the target nucleic acid. It is generally thought that the PAM sequence flanking the target nucleic acid depends on the endonuclease and the source from which the endonuclease is derived. For example, for Cas9 endonucleases that are derived from Streptococcus pyogenes, the PAM sequence is NGG, although the PAM sequences NAG and NGA may be recognized with lower efficiency. For Cas9 endonucleases derived from Staphylococcus aureus, the PAM sequence is NNGRRT. For Cas9 endonucleases that are derived from Neisseria meningitidis, the PAM sequence is NNNNGATT or the degenerate PAM sequence NNNNGHTT. See, e.g., Adli Nature Communications (2018)9:1191. Cas9 endonucleases derived from Streptococcus thermophilus, St1Cas9 and St3Cas9, the PAM sequences are NNAGAAW and NGGNG, respectively. For Cas9 endonuclease derived from Treponema denticola, the PAM sequence is NAAAAC. For Cas9 endonuclease derived from Streptococcus canis the PAM sequence is NNG. See, Chatterjee, et al. Sci. Adv. (2018) 4: eaau0766. For Cas9 endonuclease derived from Campylobacter jejuni, the PAM sequence is NNNNACAC. See, e.g., Adli Nature Communications (2018)9:1191.

In some embodiments, the Cas endonuclease is a Cpf1 nuclease. In contrast to Cas9 endonucleases, Cpf1 endonuclease generally do not require a tracrRNA sequence and recognize a PAM sequence located at the 5′ end of the target nucleic acid. For a Cpf1 nuclease, the PAM sequence is TTTN. In some embodiments, the Cas endonuclease is MAD7 (also referred to as Cpf1 nuclease from Eubacterium rectale) and the PAM sequence is YTTTN.

In some embodiments, genetically engineering a cell also comprises introducing a Cas endonuclease into the cell. In some embodiments, the Cas endonuclease and the nucleic acid encoding the gRNA are provided on the same nucleic acid (e.g., a vector). In some embodiments, the Cas endonuclease and the nucleic acid encoding the gRNA are provided on different nucleic acids (e.g., different vectors). Alternatively or in addition, the Cas endonuclease may be provided or introduced into the cell in protein form.

In some embodiments, the Cas endonuclease is a Cas9 enzyme or variant thereof. In some embodiments, the Cas9 endonuclease is derived from Streptococcus pyogenes (SpCas9), Staphylococcus aureus (SaCas9), Streptococcus canis (ScCas9), Neisseria meningitidis (NmCas9), Streptococcus thermophilus, Campylobacter jujuni (CjCas9), or Treponema denticola. In some embodiments, the nucleotide sequence encoding the Cas endonuclease may be codon optimized for expression in a host cell. In some embodiments, the endonuclease is a Cas9 homolog or ortholog.

In some embodiments, the nucleotide sequence encoding the Cas9 endonuclease is further modified to alter the activity of the protein. In some embodiments, the Cas9 endonuclease has been modified to inactivate one or more catalytic residues of the endonuclease. In some embodiments, the Cas9 endonuclease has been modified to inactivate one of the catalytic residues of the endonuclease, referred to as a “nickase” or “Cas9n”. Cas9 nickase endonucleases cleave one DNA strand of the target nucleic acid. See, e.g., Dabrowska et al. Frontiers in Neuroscience (2018) 12(75). It has been shown that one or more mutations in the RuvC and HNH catalytic domains of the enzyme may improve Cas9 efficiency. See, e.g., Sarai et al. Currently Pharma. Biotechnol. (2017) 18(13). In some embodiments, the Cas9 nickase comprises a mutation at amino acid position D10 and/or H840. In some examples, the Cas9 nickase comprises the substitution mutation D10A and/or H840A.

In some embodiments, the methods described herein involve two distinct cleavage reactions, in which one Cas9 nickase is directed to cleave one DNA strand of the target nucleic acid and a Cas9 nickase is directed to cleave the second DNA strand of the target nucleic acid.

In some embodiments, the Cas9 endonuclease is a catalytically inactive Cas9. For example, dCas9 contains mutations of catalytically active residues (D10 and H840) and does not have nuclease activity. Alternatively or in addition, the Cas9 endonuclease may be fused to another protein or portion thereof. In some embodiments, dCas9 is fused to a repressor domain, such as a KRAB domain. In some embodiments, such dCas9 fusion proteins are used with the constructs described herein for multiplexed gene repression (e.g., CRISPR interference (CRISPRi)). In some embodiments, dCas9 is fused to an activator domain, such as VP64 or VPR. In some embodiments, such dCas9 fusion proteins are used with the constructs described herein for gene activation (e.g., CRISPR activation (CRISPRa)). In some embodiments, dCas9 is fused to an epigenetic modulating domain, such as a histone demethylase domain or a histone acetyltransferase domain. In some embodiments, dCas9 is fused to a LSD1 or p300, or a portion thereof. In some embodiments, the dCas9 fusion is used for CRISPR-based epigenetic modulation. In some embodiments, dCas9 or Cas9 is fused to a Fok1 nuclease domain (referred to as “FokI-dCas9”). In some embodiments, Cas9 or dCas9 fused to a FokI nuclease domain is used for genome editing. See, e.g., Safari et al. Current Pharma. Biotechol. (2017): 18. In some embodiments, Cas9 or dCas9 is fused to a fluorescent protein (e.g., GFP, RFP, mCherry, etc.). In some embodiments, Cas9/dCas9 proteins fused to fluorescent proteins are used for labeling and/or visualization ofgenomic loci or identifying cells expressing the Cas endonuclease.

In some embodiments, the Cas endonuclease is modified to enhance specificity of the enzyme (e.g., reduce off-target effects, maintain robust on-target cleavage). In some embodiments, the Cas endonuclease is an enhanced specificity Cas9 variant (e.g., eSPCas9). See, e.g., Slaymaker et al. Science (2016) 351 (6268): 84-88. In some embodiments, the Cas endonuclease is a high fidelity Cas9 variant (e.g., SpCas9-HF1). See, e.g., Kleinstiver et al. Nature (2016) 529: 490-495.

Cas enzymes, such as Cas endonucleases, are known in the art and may be obtained from various sources and/or engineered/modified to modulate one or more activities or specificities of the enzymes. In some embodiments, the Cas enzyme has been engineered/modified to recognize one or more PAM sequence. In some embodiments, the Cas enzyme has been engineered/modified to recognize one or more PAM sequence that is different than the PAM sequence the Cas enzyme recognizes without engineering/modification. In some embodiments, the Cas enzyme has been engineered/modified to reduce off-target activity of the enzyme.

In some embodiments, the nucleotide sequence encoding the Cas endonuclease is modified further to alter the specificity of the endonuclease activity (e.g., reduce off-target cleavage, decrease the Cas endonuclease activity or lifetime in cells, increase homology-directed recombination and reduce non-homologous end joining). See, e.g., Komor et al. Cell (2017) 168: 20-36. In some embodiments, the nucleotide sequence encoding the Cas endonuclease is modified to alter the PAM recognition of the endonuclease. For example, the Cas endonuclease SpCas9 recognizes PAM sequence NGG, whereas relaxed variants of the SpCas9 comprising one or more modifications of the endonuclease (e.g., VQR SpCas9, EQR SpCas9, VRER SpCas9) may recognize the PAM sequences NGA, NGAG, NGCG. PAM recognition of a modified Cas endonuclease is considered “relaxed” if the Cas endonuclease recognizes more potential PAM sequences as compared to the Cas endonuclease that has not been modified. For example, the Cas endonuclease SaCas9 recognizes PAM sequence NNGRRT, whereas a relaxed variant of the SaCas9 comprising one or more modifications of the endonuclease (e.g., KKH SaCas9) may recognize the PAM sequence NNNRRT. In one example, the Cas endonuclease FnCas9 recognizes PAM sequence NNG, whereas a relaxed variant of the FnCas9 comprising one or more modifications of the endonuclease (e.g., RHA FnCas9) may recognize the PAM sequence YG. In one example, the Cas endonuclease is a Cpf1 endonuclease comprising substitution mutations S542R and K607R and recognize the PAM sequence TYCV. In one example, the Cas endonuclease is a Cpf1 endonuclease comprising substitution mutations S542R. K607R, and N552R and recognize the PAM sequence TATV. See, e.g., Gao et al. Nat. Biotechnol. (2017) 35(8): 789-792.

In some embodiments, the methods described herein involve genetically engineering a population of hematopoietic cells using a Cas9 nuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a gene encoding a type 1 lineage-specific cell-surface antigen in a population of hematopoietic cells using a Cas9 nuclease (or variant thereof). In some embodiments, the methods described herein involve genetically modifying or editing a CD19 gene, or genetically modifying or editing a CD33 gene, or genetically modifying or editing a CD19 gene and a CD33 gene in the population of hematopoietic cells using a Cas9 nuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutant CD19 gene in a population of hematopoietic cells using a Cas9 nuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutation in exon 2 or exon 4 of CD19 in a population of hematopoietic cells using a Cas9 nuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutant CD19 gene in a population of hematopoietic cells using a Cas9 nuclease (or variant thereof) and a guide sequence provided by any one of SEQ ID NOs: 14-26, 67, and 69-72. In some embodiments, the methods described herein involve genetically engineering a mutant CD19 gene in a population of hematopoietic cells using a Cas9 nuclease (or variant thereof) and a guide sequence provided by SEQ ID NO: 67.

In some embodiments, the methods described herein involve genetically engineering a gene encoding a type 2 lineage-specific cell-surface antigen in a population of hematopoietic cells using a Cas9 nuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutant CD33 gene in a population of hematopoietic cells using a Cas9 nuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutation in exon 2 or exon 3 of CD33 in a population of hematopoietic cells using a Cas9 nuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutant CD33 gene in a population of hematopoietic cells using a Cas9 nuclease (or variant thereof) and a guide sequence provided by any one of SEQ ID NOs: 27-50 and 68. In some embodiments, the methods described herein involve genetically engineering a mutant CD33 gene in a population of hematopoietic cells using a Cas9 nuclease (or variant thereof) and a guide sequence provided by SEQ ID NO: 68.

In some embodiments, the endonuclease is a base editor. Base editor endonuclease generally comprises a catalytically inactive Cas endonuclease fused to a function domain. See, e.g., Eid et al. Biochem. J. (2018) 475(11): 1955-1964; Rees et al. Nature Reviews Genetics (2018) 19:770-788. In some embodiments, the catalytically inactive Cas endonuclease is dCas9. In some embodiments, the endonuclease comprises a dCas9 fused to one or more uracil glycosylase inhibitor (UGI) domains. In some embodiments, the endonuclease comprises a dCas9 fused to an adenine base editor (ABE), for example an ABE evolved from the RNA adenine deaminase TadA. In some embodiments, the endonuclease comprises a dCas9 fused to cytodine deaminase enzyme (e.g., APOBEC deaminase, pmCDA1, activation-induced cytidine deaminase (AID)). In some embodiments, the catalytically inactive Cas endonuclease has reduced activity and is nCas9. In some embodiments, the endonuclease comprises a nCas9 fused to one or more uracil glycosylase inhibitor (UGI) domains. In some embodiments, the endonuclease comprises a nCas9 fused to an adenine base editor (ABE), for example an ABE evolved from the RNA adenine deaminase TadA. In some embodiments, the endonuclease comprises a nCas9 fused to cytodine deaminase enzyme (e.g., APOBEC deaminase, pmCDA1, activation-induced cytidine deaminase (AID)).

Examples of base editors include, without limitation, BE1, BE2, BE3, HF-BE3, BE4, BE4max, BE4-Gam, YE1-BE3, EE-BE3, YE2-BE3, YEE-CE3, VQR-BE3, VRER-BE3, SaBE3, SaBE4, SaBE4-Gam, Sa(KKH)-BE3, Target-AID, Target-AID-NG, xBE3, eA3A-BE3, BE-PLUS, TAM, CRISPR-X, ABE7.9, ABE7.10, ABE7.10*, xABE, ABESa, VQR-ABE, VRER-ABE, Sa(KKH)-ABE, and CRISPR-SKIP. Additional examples of base editors can be found, for example, in US Publication No. 2018/0312825A1, US Publication No. 2018/0312828A1, and PCT Publication No. WO 2018/165629A1, which are incorporated by reference herein in their entireties.

In some embodiments, the base editor has been further modified to inhibit base excision repair at the target site and induce cellular mismatch repair. Any of the Cas endonucleases described herein may be fused to a Gam domain (bacteriophage Mu protein) to protect the Cas endonuclease from degradation and exonuclease activity. See, e.g., Eid et al. Biochem. J. (2018) 475(11): 1955-1964.

In some embodiments, the methods described herein involve genetically engineering a population of hematopoietic cells using a base editor (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a gene encoding a type 1 lineage-specific cell-surface antigen in a population of hematopoietic cells using a base editor (or variant thereof). In some embodiments, the methods described herein involve genetically modifying or editing a CD19 gene, or genetically modifying or editing a CD33 gene, or genetically modifying or editing a CD19 gene and a CD33 gene in the population of hematopoietic cells using a base editor (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutant CD19 gene in a population of hematopoietic cells using a base editor (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutation in exon 2 or exon 4 of CD19 in a population of hematopoietic cells using a base editor (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutant CD19 gene in a population of hematopoietic cells using a base editor (or variant thereof) and a guide sequence provided by any one of SEQ ID NOs: 14-26, 67, and 69-72. In some embodiments, the methods described herein involve genetically engineering a mutant CD19 gene in a population of hematopoietic cells using a base editor (or variant thereof) and a guide sequence provided by SEQ ID NO: 67.

In some embodiments, the methods described herein involve genetically engineering a gene encoding a type 2 lineage-specific cell-surface antigen in a population of hematopoietic cells using a base editor (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutant CD33 gene in a population of hematopoietic cells using a base editor (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutation in exon 2 or exon 3 of CD33 in a population of hematopoietic cells using a base editor nuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutant CD33 gene in a population of hematopoietic cells using a base editor nuclease (or variant thereof) and a guide sequence provided by any one of SEQ ID NOs: 27-50 and 68. In some embodiments, the methods described herein involve genetically engineering a mutant CD33 gene in a population of hematopoietic cells using a base editor (or variant thereof) and a guide sequence provided by SEQ ID NO: 68.

In some embodiments, the Cas endonuclease belongs to class 2 type V of Cas endonuclease. Class 2 type V Cas endonucleases can be further categorized as type V-A, type V-B, type V-C, and type V-U. See, e.g., Stella et al. Nature Structural & Molecular Biology (2017). In some embodiments, the Cas endonuclease is a type V-A Cas endonuclease, such as a Cpf1 nuclease. In some embodiments, the Cas endonuclease is a type V-B Cas endonuclease, such as a C2c1 endonuclease. See, e.g., Shmakov et al. Mol Cell (2015) 60: 385-397. In some embodiments, the Cas endonuclease is Mad7.

In some embodiments, the Cas endonuclease is a Cpf1 nuclease or variant thereof. As will be appreciated by one of skill in the art, the Cas endonuclease Cpf1 nuclease may also be referred to as Cas12a. See, e.g., Strohkendl et al. Mol. Cell (2018) 71: 1-9. In some embodiments, the host cell expresses a Cpf1 nuclease derived from Provetella spp., Francisella spp, Acidaminococcus sp. (AsCpf1), Lachnospiraceae bacterium (LpCpf1), or Eubacterium rectale. In some embodiments, the nucleotide sequence encoding the Cpf1 nuclease may be codon optimized for expression in a host cell. In some embodiments, the nucleotide sequence encoding the Cpf1 endonuclease is further modified to alter the activity of the protein.

A catalytically inactive variant of Cpf1 (Cas12a) may be referred to dCas12a. As described herein, catalytically inactive variants of Cpf1 may be fused to a function domain to form a base editor. See, e.g., Rees et al. Nature Reviews Genetics (2018) 19:770-788. In some embodiments, the catalytically inactive Cas endonuclease is dCas9. In some embodiments, the endonuclease comprises a dCas12a fused to one or more uracil glycosylase inhibitor (UGI) domains. In some embodiments, the endonuclease comprises a dCas12a fused to an adenine base editor (ABE), for example an ABE evolved from the RNA adenine deaminase TadA. In some embodiments, the endonuclease comprises a dCas12a fused to cytodine deaminase enzyme (e.g. APOBEC deaminase, pmCDA1, activation-induced cytidine deaminase (AID)).

In some embodiments, the methods described herein involve genetically engineering a population of hematopoietic cells using a Cpf1 nuclease (or variant thereof. In some embodiments, the methods described herein involve genetically engineering a gene encoding a type 1 lineage-specific cell-surface antigen in a population of hematopoietic cells using a Cpf1 nuclease (or variant thereof. In some embodiments, the methods described herein involve genetically modifying or editing a CD19 gene, or genetically modifying or editing a CD33 gene, or genetically modifying or editing a CD19 gene and a CD33 gene in the population of hematopoietic cells using a Cpf1 nuclease (or variant thereof. In some embodiments, the methods described herein involve genetically engineering a mutant CD19 gene in a population of hematopoietic cells using a Cpf1 nuclease (or variant thereof. In some embodiments, the methods described herein involve genetically engineering a mutation in exon 2 or exon 4 of CD19 in a population of hematopoietic cells using a Cpf1 nuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutant CD19 gene in a population of hematopoietic cells using a Cpf1 nuclease (or variant thereof) and a guide sequence provided by any one of SEQ ID NOs: 14-26, 67, and 69-72. In some embodiments, the methods described herein involve genetically engineering a mutant CD19 gene in a population of hematopoietic cells using a Cpf1 nuclease (or variant thereof) and a guide sequence provided by SEQ ID NO: 67.

In some embodiments, the methods described herein involve genetically engineering a gene encoding a type 2 lineage-specific cell-surface antigen in a population of hematopoietic cells using a Cpf1 nuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutant CD33 gene in a population of hematopoietic cells using a Cpf1 nuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutation in exon 2 or exon 3 of CD33 in a population of hematopoietic cells using a Cpf1 nuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutant CD33 gene in a population of hematopoietic cells using a Cpf1 nuclease (or variant thereof) and a guide sequence provided by any one of SEQ ID NOs: 27-50 and 68. In some embodiments, the methods described herein involve genetically engineering a mutant CD33 gene in a population of hematopoietic cells using a Cpf1 nuclease (or variant thereof) and a guide sequence provided by SEQ ID NO: 68.

Alternatively or in addition, the Cas endonuclease may be a Cas14 endonuclease or variant thereof. In contrast to Cas9 endonucleases, Cas14 endonucleases are derived from archaea and tend to be smaller in size (e.g., 400-700 amino acids). Additionally Cas14 endonucleases do not require a PAM sequence. See, e.g., Harrington et al. Science (2018).

In some embodiments, the methods described herein involve genetically engineering a population of hematopoietic cells using a Cas14 endonuclease (or variant thereof. In some embodiments, the methods described herein involve genetically engineering a gene encoding a type 1 lineage-specific cell-surface antigen in a population of hematopoietic cells using a Cas14 endonuclease (or variant thereof. In some embodiments, the methods described herein involve genetically modifying or editing a CD19 gene, or genetically modifying or editing a CD33 gene, or genetically modifying or editing a CD19 gene and a CD33 gene in the population of hematopoietic cells using a Cas14 endonuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutant CD19 gene in a population of hematopoietic cells using a Cas14 endonuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutation in exon 2 or exon 4 of CD19 in a population of hematopoietic cells using a Cas14 endonuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutant CD19 gene in a population of hematopoietic cells using a Cas14 endonuclease (or variant thereof) and a guide sequence provided by any one of SEQ ID NOs: 14-26, 67, and 69-72. In some embodiments, the methods described herein involve genetically engineering a mutant CD19 gene in a population of hematopoietic cells using a Cas14 endonuclease (or variant thereof) and a guide sequence provided by SEQ ID NO: 67.

In some embodiments, the methods described herein involve genetically engineering a gene encoding a type 2 lineage-specific cell-surface antigen in a population of hematopoietic cells using a Cas14 endonuclease (or variant thereof. In some embodiments, the methods described herein involve genetically engineering a mutant CD33 gene in a population of hematopoietic cells using a Cas14 endonuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutation in exon 2 or exon 3 of CD33 in a population of hematopoietic cells using a Cas14 endonuclease (or variant thereof). In some embodiments, the methods described herein involve genetically engineering a mutant CD33 gene in a population of hematopoietic cells using a Cas14 endonuclease (or variant thereof) and a guide sequence provided by any one of SEQ ID NOs: 27-50 and 68. In some embodiments, the methods described herein involve genetically engineering a mutant CD33 gene in a population of hematopoietic cells using a Cas14 endonuclease (or variant thereof) and a guide sequence provided by SEQ ID NO: 68.

Any of the Cas endonucleases described herein may be modulated to regulate levels of expression and/or activity of the Cas endonuclease at a desired time. For example, it may be advantageous to increase levels of expression and/or activity of the Cas endonuclease during particular phase(s) of the cell cycle. It has been demonstrated that levels of homology-directed repair are reduced during the G1 phase of the cell cycle, therefore increasing levels of expression and/or activity of the Cas endonuclease during the S phase, G2 phase, and/or M phase may increase homology-directed repair following the Cas endonuclease editing. In some embodiments, levels of expression and/or activity of the Cas endonuclease are increased during the S phase, G2 phase, and/or M phase of the cell cycle. In one example, the Cas endonuclease fused to a the N-terminal region of human Geminin. See, e.g., Gutschner et al. Cell Rep. (2016) 14(6): 1555-1566. In some embodiments, levels of expression and/or activity of the Cas endonuclease are reduced during the G1 phase. In one example, the Cas endonuclease is modified such that it has reduced activity during the G1 phase. See, e.g., Lomova et al. Stem Cells (2018).

Alternatively or in addition, any of the Cas endonucleases described herein may be fused to an epigenetic modifier (e.g., a chromatin-modifying enzyme, e.g., DNA methylase, histone deacetylase). See, e.g., Kungulovski et al. Trends Genet. (2016) 32(2):101-113. Cas endonucleases fused to an epigenetic modifier may be referred to as “epieffectors” and may allow for temporal and/or transient endonuclease activity. In some embodiments, the Cas endonuclease is a dCas9 fused to a chromatin-modifying enzyme.

In some embodiments, the present disclosure provides compositions and methods for modifying or deleting a cell-surface lineage-specific protein in hematopoietic cells using a CRISPR/Cas9 system, wherein guide RNA sequence hybridizes to the nucleotide sequence encoding an epitope of the lineage-specific cell-surface antigen. In some embodiments, the present disclosure provides compositions and methods for modifying or deleting two or more cell-surface lineage-specific protein in hematopoietic cells using a CRISPR/Cas9 system, wherein guide RNA sequence hybridizes to the nucleotide sequence encoding an epitope of the lineage-specific cell-surface antigen. In some embodiments, the guide RNA sequence(s) hybridize to the nucleotide sequence encoding an exon of the lineage-specific cell-surface antigen. In some embodiments, one or more guide RNA sequences may hybridize to one or more intron sequences, leading to skipping of an adjacent exon. For example, two guide RNA sequence may be used to target regions in two nearby introns (e.g., intron 1 and intron 2 or intron 2 and intron 3), leading to skipping of the exon between the two introns. In some embodiments, the cell-surface lineage-specific protein is CD33 or CD19 and the gRNA hybridizes to a portion of the nucleotide sequence that encodes an epitope of CD33 or CD19. In some embodiments, the cell-surface lineage-specific protein is CD33 and the gRNA hybridizes to a portion of intron 1 or intron 2 of the nucleotide sequence encoding CD19. In some embodiments, the cell-surface lineage-specific protein is CD19 and the gRNA hybridizes to a portion of intron 1 or intron 2 of the nucleotide sequence encoding CD19.

In some embodiments, the cell-surface lineage-specific protein is CD33 and the gRNA hybridizes to a portion of the gene encoding exon2. In some embodiments, the cell-surface lineage-specific protein is CD18 and the gRNA hybridizes to a portion of the gene encoding exon3. In some embodiments, a first cell-surface lineage-specific protein is CD33 (wherein the gRNA hybridizes to a portion of the gene encoding exon2 and a second cell-surface lineage-specific protein is CD19 and the gRNA hybridizes to a portion of exon3. In some embodiments, the CD33 and/or CD19 gene is knocked out. In some embodiments, a portion of the CD33 and/or CD19 gene is knocked out.

In some embodiments, it may be desired to further genetically engineer the HSC, particularly allogeneic HSCs, to reduce the graft-versus-host effects. For example, the standard therapy for relapsed AML is hematopoietic stem cell transplantation (HSCT). However, at least one of the limiting factors for successful HSCT is graft-versus-host disease (GVHD), in which expression of the cell surface molecule CD45 has been implicated. See, e.g., Van Besie. Hematology Am. Soc. Hematol Educ Program (2013)56: Mawad, Curr. Hematol. Malig. Rep. (2013) 8(2):132, CD45RA and CD45RO are isoforms of CD45 (found on all hematopoietic cells except erythrocytes). In T lymphocytes, CD45RA is expressed on naive cells, while CD45RO is expressed on memory cells, CD45RA T cells have a high potential for reactivity against recipient-specific proteins following HSCT, resulting in GVHD. CD45 is a type 1 lineage protein, as CD45-bearing cells are required for survival; however, the antigenic portion of CD45 may be deleted from stem cells using CRISPR to prevent and/or reduce the incidence or extent of GvHD.

Also provided herein are methods of producing the genetically engineered hematopoietic cells as described herein, which carry edited genes for expressing one or more lineage-specific cell-surface antigens in mutated form. Such methods may involve providing a cell and introducing into the cell components of a CRISPR Cas system for genome editing. In some embodiments, a nucleic acid that comprises a CRISPR-Cas guide RNA (gRNA) that hybridizes or is predicted to hybridize to a portion of the nucleotide sequence that encodes the lineage-specific cell-surface antigen is introduced into the cell. In some embodiments, the gRNA is introduced into the cell on a vector. In some embodiments, a Cas endonuclease is introduced into the cell. In some embodiments, the Cas endonuclease is introduced into the cell as a nucleic acid encoding a Cas endonuclease. In some embodiments, the gRNA and a nucleotide sequence encoding a Cas endonuclease are introduced into the cell on the same nucleic acid (e.g., the same vector). In some embodiments, the Cas endonuclease is introduced into the cell in the form of a protein. In some embodiments, the Cas endonuclease and the gRNA are pre-formed in vitro and are introduced to the cell in as a ribonucleoprotein complex.

In some embodiments, multiple gRNAs are introduced into the cell. In some embodiments, the two or more guide RNAs are transfected into cells in equimolar amounts. In some embodiments, the two or more guide RNAs are provided in amounts that are not equimolar. In some embodiments, the two or more guide RNAs are provided in amounts that are optimized so that editing of each target occurs at equal frequency. In some embodiments, the two or more guide RNAs are provided in amounts that are optimized so that editing of each target occurs at optimal frequency.

In some embodiments, multiple gRNAs are allowed to form gRNA-RNP complexes in the same reaction. In some embodiments, two or more gRNA-RNP complexes are formed in separate reactions. The RNP complexes with the two or more guide RNAs can be transfected together or separately. For example, Cas9-CD19gRNA-19 RNPs and Cas9-CD33_gRNA-37 RNPs can be formed separately in two isolated incubations or together in one incubation and can be transfected together or separately, e.g., concurrently.

In some embodiments, the two or more guides are transfected concurrently with each other. In some embodiments, the two or more guides are provided sequentially or consecutively, i.e., in two or more separate transfections. For example, Cas9-CD19_gRNA-RNPs and Cas9-CD33 gRNA RNPs can be transfected together. e.g., in equimolar amounts or another optimal ratio. In some examples, RNPs comprising Cas9 and any one of the CD19 gRNAs provided by SEQ ID NOs: 14-26, 67, 69-72 are transfected with RNPs comprising Cas9 and any one of the CD33 gRNAs provided by SEQ ID NOs: 22-50 and 68. Alternatively, Cas9-CD19_gRNA-RNPs and Cas9-CD33 gRNA RNPs can be transfected sequentially, e.g., either first Cas9-CD19gRNA-RNPs and then Cas9-CD33 gRNA RNPs or first Cas9-CD33_gRNA-RNPs and then Cas9-CD19 gRNA RNPs. In some examples, RNPs comprising Cas9 and any one of the CD19 gRNAs provided by SEQ ID NOs: 14-26, 67, 69-72 are transfected sequentially (e.g., prior to or after) RNPs comprising Cas9 and any one of the CD33 gRNAs provided by SEQ ID NOs: 22-50 and 68.

Vectors of the present disclosure can drive the expression of one or more sequences in mammalian cells using a mammalian expression vector. Examples of mammalian expression vectors include pCDM8 (Seed, Nature (1987) 329: 840) and pMT2PC (Kaufman, et al., EMBO J. (1987) 6: 187). When used in mammalian cells, the expression vector's control functions are typically provided by one or more regulatory elements. For example, commonly used promoters are derived from polyoma, adenovirus 2, cytomegalovirus, simian virus 40, and others disclosed herein and known in the art. For other suitable expression systems for both prokaryotic and eukaryotic cells see, e.g., Chapters 16 and 17 of Sambrook, et al., MOLECULAR CLONING: A LABORATORY MANUAL. 2nd eds., Cold Spring Harbor Laboratory, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989.

The vectors of the present disclosure are capable of directing expression of the nucleic acid preferentially in a particular cell type (e.g., tissue-specific regulatory elements are used to express the nucleic acid). Such regulatory elements include promoters that may be tissue specific or cell specific. The term “tissue-specific” as it applies to a promoter refers to a promoter that is capable of directing selective expression of a nucleotide sequence of interest to a specific type of tissue (e.g., seeds) in the relative absence of expression of the same nucleotide sequence of interest in a different type of tissue. The term “cell type specific” as applied to a promoter refers to a promoter that is capable of directing selective expression of a nucleotide sequence of interest in a specific type of cell in the relative absence of expression of the same nucleotide sequence of interest in a different type of cell within the same tissue. The term “cell type specific” when applied to a promoter also means a promoter capable of promoting selective expression of a nucleotide sequence of interest in a region within a single tissue. Cell type specificity of a promoter may be assessed using methods well known in the art, e.g., immunohistochemical staining.

Conventional viral and non-viral based gene transfer methods can be used to introduce nucleic acids encoding CRISPR-Cas9 in mammalian cells or target tissues. Such methods can be used to administer nucleic acids encoding components of a CRISPR-Cas system to cells in culture, or in a host organism. Non-viral vector delivery systems include DNA plasmids, RNA (e.g., a transcript of a vector described herein), naked nucleic acid, and nucleic acid complexed with a delivery vehicle. In some embodiments, nucleic acids encoding CRISPR/Cas9 are introduced by transfection (e.g., electroporation, microinjection. In some embodiments, nucleic acids encoding CRISPR/Cas9 are introduced by nanoparticle delivery, e.g., cationic nanocarriers.

Viral vector delivery systems include DNA and RNA viruses, which have either episomal or integrated genomes after delivery to the cell.

Viral vectors can be administered directly to patients (in vivo) or they can be used to manipulate cells in vitro or ex vivo, where the modified cells may be administered to patients. In one embodiment, the present disclosure utilizes viral based systems including, but not limited to retroviral, lentivirus, adenoviral, adeno-associated and herpes simplex virus vectors for gene transfer. Furthermore, the present disclosure provides vectors capable of integration in the host genome, such as retrovirus or lentivirus. Preferably, the vector used for the expression of a CRISPR-Cas system of the present disclosure is a lentiviral vector.

In one embodiment, the disclosure provides for introducing one or more vectors encoding CRISPR-Cas into eukaryotic cell. The cell can be a cancer cell. Alternatively, the cell is a hematopoietic cell, such as a hematopoietic stem cell. Examples of stem cells include pluripotent, multipotent and unipotent stem cells. Examples of pluripotent stem cells include embryonic stem cells, embryonic germ cells, embryonic carcinoma cells and induced pluripotent stem cells (iPSCs). In a preferred embodiment, the disclosure provides introducing CRISPR-Cas9 into a hematopoietic stem cell.

The vectors of the present disclosure are delivered to the eukaryotic cell in a subject. Modification of the eukaryotic cells via CRISPR/Cas9 system can takes place in a cell culture, where the method comprises isolating the eukaryotic cell from a subject prior to the modification. In some embodiments, the method further comprises returning said eukaryotic cell and/or cells derived therefrom to the subject.

In some embodiments, the gRNA is introduced into the cell in the form of a vector. In some embodiments, the gRNA and a nucleotide sequence encoding a Cas endonuclease are introduced into the cell on the same nucleic acid (e.g., the same vector). In some embodiments, the gRNA is introduced into the cell in the form of an RNA. In some embodiments, the gRNA may comprise one or more modifications, for example, to enhance stability of the gRNA, reduce off-target activity, increase editing efficiency. Examples of modifications include, without limitation, base modifications, backbone modifications, and modifications to the length of the gRNA. For example, it has been demonstrated that extending the length of a gRNA at the 5′end and/or introducing one or more chemical modification may increase editing efficiency. See, e.g., Park et al. Nature Communications (2018) 9:3313. Moon et al. Nature Communications (2018) 9: 3651. Additionally, incorporation of nucleic acids or locked nucleic acids have been found to increase specificity of genomic editing. See, e.g., Cromwell, et al. Nature Communications (2018) 9: 1448. See, e.g., Safari et al. Current Pharm. Biotechnol. (2017) 18:13. In some embodiments, the gRNA may comprise one or more modification chosen from phosphorothioate backbone modification, 2′-O-Me-modified sugars (e.g., at one or both of the 3′ and 5′ termini), 2′F-modified sugar, replacement of the ribose sugar with the bicyclic nucleotide-cEt, 3′thioPACE (MSP), or any combination thereof. Suitable gRNA modifications are described, e.g., in Rahdar et al. PNAS Dec. 22, 2015 112 (51) E7110-E7117 and Hendel et al., Nat Biotechnol. 2015 September; 33(9): 985-989, each of which is incorporated herein by reference in its entirety. In some embodiments, a gRNA described herein comprises one or more 2′-O-methyl-3′-phosphorothioate nucleotides, e.g., at least 2, 3, 4, 5, or 6 2′-O-methyl-3′-phosphorothioate nucleotides. In some embodiments, a gRNA described herein comprises modified nucleotides (e.g., 2′-O-methyl-3′-phosphorothioate nucleotides) at the three terminal positions and the 5′ end and/or at the three terminal positions and the 3′ end.

In some embodiments, the gRNA comprises one or more modified bases (e.g. 2′ O-methyl nucleotides). In some embodiments, the gRNA comprises one or more modified uracil base. In some embodiments, the gRNA comprises one or more modified adenine base. In some embodiments, the gRNA comprises one or more modified guanine base. In some embodiments, the gRNA comprises one or more modified cytosine base.

In some embodiments, the gRNA comprises one or more modified intemucleotide linkages such as, for example, phosphorothioate, phosphoramidate, and O′methyl ribose or deoxyribose residue.

In some embodiments, the gRNA comprises an extension of about 10 nucleotides to 100 nucleotides at the 3′ end and/or 5′end of the gRNA. In some embodiments, the gRNA comprises an extension of about 10 nucleotides to 100 nucleotides, about 20 nucleotides to 90 nucleotides, about 30 nucleotides to 80 nucleotides, about 40 nucleotides to 70 nucleotides, about 40 nucleotides to 60 nucleotides, about 50 nucleotides to 60 nucleotides.

In some embodiments, the Cas endonuclease and the gRNA are pre-formed in vitro and are introduced to the cell in as a ribonucleoprotein complex. Examples of mechanisms to introduce a ribonucleoprotein complex comprising the Cas endonuclease and the gRNA include, without limitation, electroporation, cationic lipids, DNA nanoclew, and cell penetrating peptides. See, e.g., Safari et al. Current Pharma. Biotechnol. (2017) 18(13): Yin et al. Nature Review Drug Discovery (2017) 16: 387-399.

Any of the CRISPR/Cas systems described herein may be further optimized to increase selectivity of genomic editing, for example by enhancing homologous recombination. See, e.g., Komor et al. Cell (2017) 168: 20-36. For example, in some embodiments, CRISPR/Cas system is optimized to inhibit nonhomologous end joining and/or promote homologous directed recombination.

A number of small molecules have been identified to modulate Cas endonuclease genome editing. In some embodiments, the cells are contacted with one or more small molecule to enhance Cas endonuclease genome editing. In some embodiments, a subject is administered one or more small molecule to enhance Cas endonuclease genome editing. In some embodiments, the cells are contacted with one or more small molecule to inhibit nonhomologous end joining and/or promote homologous directed recombination. Examples of small molecules that may modulate Cas endonuclease genome editing include, without limitation L755507, Brefeldin A, ligase IV inhibitor SCR7, VE-822, AZD-7762. See, e.g., Hu et al. Cell Chem. Biol. (2016) 23: 57-73; Yu et al. Cell Stem Cell (2015) 16: 142-147; Chu et al. Nat. Biotechnol. (2015) 33: 543-548: Maruyama et al. Nat. Biotechnol. (2015) 33: 538-542; and Ma et al. Nature Communications (2018) 9:1303.

In some embodiments, any of the Cas endonucleases may be used with a donor single stranded DNA designed to anneal with the DNA strand initially released from the Cas endonucleases.

In some embodiments, it is desirable to temporally regulate genomic editing. For example, in some embodiments, the expression and/or activity of a Cas endonuclease may be regulated to induce genomic editing at a desired time. In some embodiments, cells containing any of the CRISPR/Cas systems described herein may be allowed to engraft into a subject and then expression and/or activity the Cas endonuclease may be induced. Alternatively or in addition, as described herein, the Cas endonuclease may be fused to an epigenetic modifier (e.g., a chromatin-modifying enzyme, e.g., DNA methylase, histone deacetylase).

(B) Genetically Engineered Hematopoietic Cells Expressing CD19 Mutants and/or CD33 Mutants

In some embodiments, the genetically engineered hematopoietic cells may have edited CD19 gene, CD33 gene, or both, which are designed to express mutated CD19, CD33, or both. In some instances, the mutated CD19 and/or CD33 include mutations or deletions in one or more non-essential epitopes so as to retain (at least partially) the bioactivity of CD19 and/or CD33.

(i) Genetically Engineered Hematopoietic Cells Expressing CD19 Mutants

In some examples, provided herein are variants of CD19, which may comprise a deletion or mutation of a fragment of the protein that is encoded by any one of the exons of CD19, or deletion or mutation in a non-essential epitope of CD19. The whole sequence of the CD19 gene, containing fifteen exons, is known in the art. See. e.g., GenBank accession no. NC_000016. For example, one or more epitopes located in the region encoded by exon 2 the CD19 gene may be deleted or mutated. Certain modifications to the region of the CD19 gene encoding exon 2 have been shown to result in successful CD19 protein expression, membrane localization, and partial maintenance of protein function (Sotillo et al. Cancer Discovery. (2015) 5: 1282-1295). For example, missense or frameshift mutations in exon 2 of the CD19 gene, or alternatively, modifications that permanently or transiently reduce expression of the splicing factor SRSF3, which is involved in retention of CD19 exon 2, may reduce CD19 expression in vivo. In some embodiments, one or more epitopes located in the region encoded by exon 2 of the CD19 gene are mutated or deleted. For example, the FMC63 epitope of CD19, which is a known target of CD19-targeted CAR therapies may be mutated or deleted (Sotillo et al. Cancer Discovery. (2015) 5: 1282-129; Nicholson et al. Mol Immunol. (1997) 34:1157-1165: Zola et al. Immunol Cell Biol. (1991) 69:411-422).

In some examples, one or more epitopes located in the region encoded by exon 4 of the CD19 gene may be deleted or mutated.

In some embodiments, exon 2 of CD19 is mutated or deleted. In some embodiments, exon 4 of CD19 is mutated or deleted. The amino acid sequence of an exemplary human CD19 is provided below with the fragment encoded by exon 2 underlined and the fragment encoded by exon 4 in italics (SEQ ID NO:51).

MPPPRLLFFLLFLTPMEVRPEEPLVVKVEEGDNAVLQCLKGTSDGPTQQLTWSRESPLKPFLKLSLGL PGLGIHMRPLAIWLFIFNVSQQMGGFYLCQPGPPSEKAWQPGWTVNVEGSGELFRWNVSDLGGLGCGL KNRSSEGPSSPSGKLMSPKLYVWAKDRPEIWEGEPPCLPPRDSLNQSLSQDLTMAPGSTLWLSCGVPP DSVSRGPLSWTHVHPKGPKSLLSLELKDDRPARDMWVMETGLLLPRATAQDAGKYYCHRGNLTMSFHL EITARPVLWHWLLRTGGWKVSAVTLAYLIFCLCSLVGILHLQRALVLRRKRKRMTDPTRRFFKVTPPP GSGPQNQYGNVLSLPTPTSGLGRAQRWAAGLGGTAPSYGNPSSDVQADGALGSRSPPGVGPEEEEGEG YEEPDSEEDSEFYENDSNLGQDQLSQDGSGYENPEDEPLGPEDEDSFSNAESYENEDEELTQPVARTM DFLSPHGSAWDPSREATSLGSQSYEDMRGILYAAPQLRSIRGQPGPNHEEDADSYENMDNPDGPDPAW GGGGRMGTWSTR

CD19 Full-Length

mRNA (underlined = exon 2; italics = exon 4) AUGCCACCUCCUCGCCUCCUCUUCUUCCUCCUCUUCCUCACCCCCAUGGAAGUCAGGCCCGAGGAACCU CUAGUGGUGAAGGUGGAAGAGGGAGAUAACGCUGUGCUGCAGUGCCUGAAGGGGACCUCAGAUGGCCCCACUCAG CAGCUGACCUGGUCUCGGGAGUCCCCGCUUAAACCCUUCUUAAAACUCAGCCUGGGGCUGCCAGGCCUGGGAAUC CACAUGAGGCCCCUGGCCAUCUGGCUUUUCAUCUUCAACGUCUCUCAACAGAUGGGGGGCUUCUACCUGUGCCAG CCGGGGCCCCCCUCUGAGAAGGCCUGGCAGCCUGGCUGGACAGUCAAUGUGGAGGGCAGCGGGGAGCUGUUCCGG UGGAAUGUUUCGGACCUAGGUGGCCUGGGCUGUGGCCUGAAGAACAGGUCCUCAGAGGGCCCCAGCUCCCCUUCC GGGAAGCUCAUGAGCCCCAAGCUGUAUGUGUGGGCCAAAGACCGCCCUGAGAUCUGGGAGGGAGAGCCUCCGUGU CUCCCACCGAGGGACAGCCUGAACCAGAGCCUCAGCCAGGACCUCACCAUGGCCCCUGGCUCCACACUCUGGCUG UCCUGUGGGGUACCCCCUGACUCUGUGUCCAGGGGCCCCCUCUCCUGGACCCAUGUGCACCCCAAGGGGCCUAAG UCAUUGCUGAGCCUAGAGCUGAAGGACGAUCGCCCGGCCAGAGAUAUGUGGGUAAUGGAGACGGGUCUGUUGUUG CCCCGGGCCACAGCUCAAGACGCUGGAAAGUAUUAUUGUCACCGUGGCAACCUGACCAUGUCAUUCCACCUGGAG AUCACUGCUCGGCCAGUACUAUGGCACUGGCUGCUGAGGACUGGUGGCUGGAAGGUCUCAGCUGUGACUUUGGCU UAUCUGAUCUUCUGCCUGUGUUCCCUUGUGGGCAUUCUUCAUCUUCAAAGAGCCCUGGUCCUGAGGAGGAAAAGA AAGCGAAUGACUGACCCCACCAGGAGAUUCUUCAAAGUGACGCCUCCCCCAGGAAGCGGGCCCCAGAACCAGUAC GGGAACGUGCUGUCUCUCCCCACACCCACCUCAGGCCUCGGACGCGCCCAGCGUUGGGCCGCAGGCCUGGGGGGC ACUGCCCCGUCUUAUGGAAACCCGAGCAGCGACGUCCAGGCGGAUGGAGCCUUGGGGUCCCGGAGCCCGCCGGGA GUGGGCCCAGAAGAAGAGGAAGGGGAGGGCUAUGAGGAACCUGACAGUGAGGAGGACUCCGAGUUCUAUGAGAAC GACUCCAACCUUGGGCAGGACCAGCUCUCCCAGGAUGGCAGCGGCUACGAGAACCCUGAGGAUGAGCCCCUGGGU CCUGAGGAUGAAGACUCCUUCUCCAACGCUGAGUCUUAUGAGAACGAGGAUGAAGAGCUGACCCAGCCGGUCGCC AGGACAAUGGACUUCCUGAGCCCUCAUGGGUCAGCCUGGGACCCCAGCCGGGAAGCAACCUCCCUGGCAGGGUCC CAGUCCUAUGAGGAUAUGAGAGGAAUCCUGUAUGCAGCCCCCCAGCUCCGCUCCAUUCGGGGCCAGCCUGGACCC AAUCAUGAGGAAGAUGCAGACUCUUAUGAGAACAUGGAUAAUCCCGAUGGGCCAGACCCAGCCUGGGGAGGAGGG GGCCGCAUGGGCACCUGGAGCACCAGGUGA

In some examples, the genetically engineered hematopoietic cells have a genetically engineered CD19 gene (e.g., a genetically engineered endogenous CD19 gene), which expresses a CD19 mutant having the fragment encoded by exon 2 deleted (CD19ex2). An exemplary amino acid sequence of such a CD19 mutant is provided below (the junction of exon 1-encoded fragment and exon-3 encoded fragment is shown in boldface):

(SEQ ID NO: 52) MPPPRRLFFLLFLTPMEVRPEEPLVVRVEGELFRWNVSDEGGLGCGLKNRSSEGPSSPSGKLMSPKLY VWAKDRPEIWEGEPPCLPPRDSLNQSLSQDLTMAPGSTLWLSCGVPPDSVSROPLSWTHVHPKGPKSL LSLELKDDRPARDMWVMETGLELPRATAQDAGNYYCHRONLTMSFHLEITARPVLWHWELRTGOWKVS AVTLAYLIFCLCSLVGILHLQRALVIRRKRKRMTDPTRREFKVTPPPGSGPQNQYGNVLSLPTPTSGL GRAORWAAGLGGTAPSYGNPSSDVOADGAIGSRSPPGVGPEEEEGEGYEEPDSEEDSEFYENDSNLGQ DQLSUGSGYENPEDEPLOPEDEDSFSNAESYENEDEELTUVARTMDFLSPNGSAWDPSREATSLAG SQSYEDMRGILYILAPQLRSIRGQPOPNHEEDADSYENMDNPDGPDPAWOGOGRMOTWSTR mRNA ex2 delete AUGCCACCUCCUCGCCUCCUCUUCUUCCUCCUCUUCCUCACCCCCAUGGAAGUCAGGCCCGAGGAACCUCUAGUG GUGAAGGUGGAAGGGGAGCUGUUCCGGUGGAAUGUUUCGGACCUAGGUGGCCUGGGCUGUGGCCUGAAGAACAGG UCCUCAGAGGGCCCCAGCUCCCCUUCCGGGAAGCUCAUGAGCCCCAAGCUGUAUGUGUGGGCCAAAGACCGCCCU GAGAUCUGGGAGGGAGAGCCUCCGUGUCUCCCACCGAGGGACAGCCUGAACCAGAGCCUCAGCCAGGACCUCACC AUGGCCCCUGGCUCCACACUCUGGCUGUCCUGUGGGGUACCCCCUGACUCUGUGUCCAGGGGCCCCCUCUCCUGG ACCCAUGUGCACCCCAAGGGGCCUAAGUCAUUGCUGAGCCUAGAGCUGAAGGACGAUCGCCCGGCCAGAGAUAUG UGGGUAAUGGAGACGGGUCUGUUGUUGCCCCGGGCCACAGCUCAAGACGCUGGAAAGUAUUAUUGUCACCGUGGC AACCUGACCAUGUCAUUCCACCUGGAGAUCACUGCUCGGCCAGUACUAUGGCACUGGCUGCUGAGGACUGGUGGC UGGAAGGUCUCAGCUGUGACUUUGGCUUAUCUGAUCUUCUGCCUGUGUUCCCUUGUGGGCAUUCUUCAUCUUCAA AGAGCCCUGGUCCUGAGGAGGAAAAGAAAGCGAAUGACUGACCCCACCAGGAGAUUCUUCAAAGUGACGCCUCCC CCAGGAAGCGGGCCCCAGAACCAGUACGGGAACGUGCUGUCUCUCCCCACACCCACCUCAGGCCUCGGACGCGCC CAGCGUUGGGCCGCAGGCCUGGGGGGCACUGCCCCGUCUUAUGGAAACCCGAGCAGCGACGUCCAGGCGGAUGGA GCCUUGGGGUCCCGGAGCCCGCCGGGAGUGGGCCCAGAAGAAGAGGAAGGGGAGGGCUAUGAGGAACCUGACAGU GAGGAGGACUCCGAGUUCUAUGAGAACGACUCCAACCUUGGGCAGGACCAGCUCUCCCAGGAUGGCAGCGGCUAC GAGAACCCUGAGGAUGAGCCCCUGGGUCCUGAGGAUGAAGACUCCUUCUCCAACGCUGAGUCUUAUGAGAACGAG GAUGAAGAGCUGACCCAGCCGGUCGCCAGGACAAUGGACUUCCUGAGCCCUCAUGGGUCAGCCUGGGACCCCAGC CGGGAAGCAACCUCCCUGGCAGGGUCCCAGUCCUAUGAGGAUAUGAGAGGAAUCCUGUAUGCAGCCCCCCAGCUC CGCUCCAUUCGGGGCCAGCCUGGACCCAAUCAUGAGGAAGAUGCAGACUCUUAUGAGAACAUGGAUAAUCCCGAU GGGCCAGACCCAGCCUGGGGAGGAGGGGGCCGCAUGGGCACCUGGAGCACCAGGUGA

In some embodiments, exon 4 of CD19 is mutated or deleted. In some examples, the genetically engineered hematopoietic cells have a genetically engineered CD19 gene (e.g., a genetically engineered endogenous CD19 gene), which expresses a CD19 mutant having the fragment encoded by exon 4 deleted (CD19ex4). An exemplary amino acid sequence of such a CD19 mutant is provided below:

(SEQ. ID NO: 73) MPPPRLLFFLLFLTPMEVRPEEPLVVKVEEGDNAVLQCLKGTSDGPTQQLTWSRESPLKPFLKLSLGLPGLGIHM RPLAIWLFIFNVSQQMGGFYLCQPGPPSEKAWQPGWTVNVEGSGELFRWNVSDLGGLGCGLKNRSSEGPSSPSGK LMSPKLYVWAKDRPEIWEGEPPCLPPRDSLNQSLSQVLWHWLLRTGGWKVSAVTLAYLIFCLCSLVGILHLQRAL VLRRKRKRMTDPTRRFFKVTPPPGSGPQNQYGNVLSLPTPTSGLGRAQRWAAGLGGTAPSYGNPSSDVQADGALG SRSPPGVGPEEEEGEGYEEPDSEEDSEFYENDSNLGQDQLSQDGSGYENPEDEPLGPEDEDSFSNAESYENEDEE LTQPVARTMDFLSPHGSAWDPSREATSLAGSQSYEDMRGILYAAPQLRSIRGQPGPNHEEDADSYENMDNPDGPD PAWGGGGRMGTWSTR mRNA ex4 delete ATGCCACCTCCTCGCCTCCTCTTCTTCCTCCTCTTCCTCACCCCCATGGAAGTCAGGCCCGAGGAACCTCTAGTG GTGAAGGTGGAAGAGGGAGATAACGCTGTGCTGCAGTGCCTCAAGGGGACCTCAGATGGCCCCACTCAGCAGCTG ACCTGGTCTCGGGAGTCCCCGCTTAAACCCTTCTTAAAACTCAGCCTGGGGCTGCCAGGCCTGGGAATCCACATG AGGCCCCTGGCCATCTGGCTTTTCATCTTCAACGTCTCTCAACAGATGGGGGGCTTCTACCTGTGCCAGCCGGGG CCCCCCTCTGAGAAGGCCTGGCAGCCTGGCTGGACAGTCAATGTGGAGGGCAGCGGGGAGCTGTTCCGGTGGAAT GTTTCGGACCTAGGTGGCCTGGGCTGTGGCCTGAAGAACAGGTCCTCAGAGGGCCCCAGCTCCCCTTCCGGGAAG CTCATGAGCCCCAAGCTGTATGTGTGGGCCAAAGACCGCCCTGAGATCTGGGAGGGAGAGCCTCCGTGTCTCCCA CCGAGGGACAGCCTGAACCAGAGCCTCAGCCAGGTACTATGGCACTGGCTGCTGAGGACTGGTGGCTGGAAGGTC TCAGCTGTGACTTTGGCTTATCTGATCTTCTGCCTGTGTTCCCTTGTGGGCATTCTTCATCTTCAAAGAGCCCTG GTCCTGAGGAGGAAAAGAAAGCGAATGACTGACCCCACCAGGAGATTCTTCAAAGTGACGCCTCCCCCAGGAAGC GGGCCCCAGAACCAGTACGGGAACGTGCTGTCTCTCCCCACACCCACCTCAGGCCTCGGACGCGCCCAGCGTTGG GCCGCAGGCCTGGGGGGCACTGCCCCGTCTTATGGAAACCCGAGCAGCGACGTCCAGGCGGATGGAGCCTTGGGG TCCCGGAGCCCGCCGGGAGTGGGCCCAGAAGAAGAGGAAGGGGAGGGCTATGAGGAACCTGACAGTGAGGAGGAC TCCGAGTTCTATGAGAACGACTCCAACCTTGGGCAGGACCAGCTCTCCCAGGATGGCAGCGGCTACGAGAACCCT GAGGATGAGCCCCTGGGTCCTGAGGATGAAGACTCCTTCTCCAACGCTGAGTCTTATGAGAACGAGGATGAAGAG CTGACCCAGCCGGTCGCCAGGACAATGGACTTCCTGAGCCCTCATGGGTCAGCCTGGGACCCCAGCCGGGAAGCA ACCTCCCTGGCAGGGTCCCAGTCCTATGAGGATATGAGAGGAATCCTGTATGCAGCCCCCCAGCTCCGCTCCATT CGGGGCCAGCCTGGACCCAATCATGAGGAAGATGCAGACTCTTATGAGAACATGGATAATCCCGATGGGCCAGAC CCAGCCTGGGGAGGAGGGGGCCGCATGGGCACCTGGAGCACCAGGTGA

Genetically engineered hematopoietic stem cells carrying an edited CD19 gene that expresses this CD19 mutant are also within the scope of the present disclosure.

Genetically engineered hematopoietic stem cells carrying an edited CD19 gene that expresses this CD19 mutant are also within the scope of the present disclosure. Such cells may be a homogenous population containing cells expressing the same CD19 mutant (e.g., CD19ex2, CD19ex4). Alternatively, the cells may be a heterogeneous population containing cells expressing different CD19 mutants (which may due to heterogeneous editing/repairing events inside cells) or cells that do not express CD19 (CD19KO). In specific examples, the genetically engineered HSCs may be a heterogeneous population containing cells expressing CD19ex2 and cells that do not express CD19 (CD19KO). In some specific examples, the genetically engineered HSCs may be a heterogeneous population containing cells expressing CD19ex4 and cells that do not express CD19 (CD19KO).

Genetically engineered hematopoietic stem cells having edited a CD19 gene can be prepared by a suitable genome editing method, such as those known in the art or disclosed herein. In some embodiments, the genetically engineered hematopoietic stem cells described herein can be generated using the CRISPR approach. See discussions herein. In certain examples, specific guide RNAs targeting a fragment of the CD19 gene (an exon sequence or an intron sequence) can be used in the CRISPR method. Exemplary gRNAs for editing the CD19 gene (e.g., deletion of exon 2, exon 4) are provided in Example 1, Table 3, and Example 3 below.

In some examples, multiple gRNAs can be used for editing the CD19 gene via CRISPR. Different combinations of gRNAs, e.g., selected from those listed in Table 3, can be used in the multiplex approach. In one example, the pair of gRNA 6 (AGCAGAGGACTCCAAAAGCT; SEQ ID NO: 18) and gRNA 14 (CCATGGACAGAAGAGGTCCG; SEQ ID NO: 24) are used for editing CD19 via CRISPR. Also provided herein are methods of genetically editing CD19 in hematopoietic cells (e.g., HSCs) via CRISPR, using one or more of the gRNAs described herein, for example, the pair of gRNA6+gRNA14 or the pair of gRNA 23+gRNA 24.

Because of the mechanism of Cas9 cutting and DNA repair, there will be a spectrum of repair events including small insertions on 1-2 nucleotides and occasionally longer deletions. Representative sequences of repaired CD19exon 2 deletion products (intron 1-intron 2 displayed) are shown below (SEQ ID Nos:53-55):

Example Comments Repair Sequence Length #1 Ligation: CCGGCTCCTCCACTCCCagcccgCGGCCACAATGGAGCTGGAG 0 #2 Insertion: CCGGCTCCTCCACTCCCagcTccgCGGCCACAATGGAGCTGGAG +1 #3 Deletion: -----------------------gCGGCCACAATGGAGCTGGAG −133 Partial loss Exon 1 Despite the heterogeneity at the genomic DNA level, the RNA transcripts provided from the edited CD19 gene all encode a CD19 mutant having the fragment encoded by exon 2 deleted.

(ii) Genetically Engineered Hematopoietic Cells Expressing CD33 Mutants

In some embodiments, the lineage-specific cell-surface protein is CD33. As will be known to one of ordinary skill in the art, CD33 is encoded by seven exons, including the alternatively spliced exons 7A and 7B (Brinkman-Van der Linden et al. Mol Cell. Biol. (2003) 23: 4199-4206). Further, the CD33 gene encodes two isoforms, one of which retains exon 2, referred to as CD33M, and one that excludes exon 2, referred to as CD33m (FIG. 17).

Exemplary amino acid sequences of the 7A and 7B splicing isoforms are provided below:

CD33N-7A: Amino Acid (underlined = exon 2; italicized = exon 7A) (SEO ID NO: I) MPLLLLLPLLWAGALAMDPNFWLQVQESVTVQEGLCVLVPCTFFHPIP YYDKNSPVHGYWFREGAIISRDSPVATNKLDQEVQEETQGRFRLLGDP SRNNCSLSIVDARRRDNGSYFFRMERGSTKYSYKSPQLSVHVTDLTHR PKILIPGTLEPGHSKNLTCSVSWACEQGTPPIFSWLSAAPTSLGPRTT HSSVLIITPRPQDHGTNLTCQVKFAGAGVTTERTIQLNVTYVPQNPTT GIFPGDGSGKQETRAGVVHGAIGGAGVTALLALCLCLIFFIVKTHRRK AARTAVGRNDTHPTTGSASPKHQKKSKLHGPTETSSCSGAAPTVEMDE ELHYASLNFHGMNPSKDTSTEYSEVRTQ CD33-M; transcript variant 1 mRNA, NM_001772 (underlined = exon 2; italicized = axon 7A) AUGCCGCUGCUGCUACUGCUGCCCCUGCUGUGGGCAGGGGCCCUGGCU AUGGAUCCAAAUUUCUGGCUGCAAGUGCAGGAGUCAGUGACGGUACAG GAGGGUUUGUGCGUCCUCGUGCCCUGCACUUUCUUCCAUCCCAUACCC UACUACGACAAGAACUCCCCAGUUCAUGGUUACUGGUUCCGGGAAGGA GCCAUUAUAUCCAGGGACUCUCCAGUGGCCACAAACAAGCUAGAUCAA GAAGUACAGGAGGAGACUCAGGGCAGAUUCCGCCUCCUUGGGGAUCCC AGUAGGAACAACUGCUCCCUGAGCAUCGUAGACGCCAGGAGGAGGGAU AAUGGUUCAUACUUCUUUCGGAUGGAGAGAGGAAGUACCAAAUACAGU UACAAAUCUCCCCAGCUCUCUGUGCAUGUGACAGACUUGACCCACAGG CCCAAAAUCCUCAUCCCUGGCACUCUAGAACCCGGCCACUCCAAAAAC CUGACCUGCUCUGUGUCCUGGGCCUGUGAGCAGGGAACACCCCCGAUC UUCUCCUGGUUGUCAGCUGCCCCCACCUCCCUGGGCCCCAGGACUACU CACUCCUCGGUGCUCAUAAUCACCCCACGGCCCCAGGACCACGGCACC AACCUGACCUGUCAGGUGAAGUUCGCUGGAGCUGGUGUGACUACGGAG AGAACCAUCCAGCUCAACGUCACCUAUGUUCCACAGAACCCAACAACU GGUAUCUUUCCAGGAGAUGGCUCAGGGAAACAAGAGACCAGAGCAGGA GUGGUUCAUGGGGCCAUUGGAGGAGCUGGUGUUACAGCCCUGCUCGCU CUUUGUCUCUGCCUCAUCUUCUUCAUAGUGAAGACCCACAGGAGGAAA GCAGCCAGGACAGCAGUGGGCAGGAAUGACACCCACCCUACCACAGGG UCAGCCUCCCCGAAACACCAGAAGAAGUCCAAGUUACAUGGCCCCACU GAAACCUCAAGCUGUUCAGGUGCCGCCCCUACUGUGGAGAUGGAUGAG GAGCUGCAUUAUGCUUCCCUCAACUUUCAUGGGAUGAAUCCUUCCAAG GACACCUCCACCGAAUACUCAGAGGUCAGGACCCAGUGA CD33m-7A: Amino Acid (italicized = exon 74; SEQ ID NO: 56) MPLLLLLPLLWADLTHRPKILIPGTLEPGHSKNLTCSVSWACEQGTPP IFSWLSAAPTSLGPRTTHSSVLIITPRPODHGTNLTCQVKFAGAGVTT ERTIQLNVTYVPQNPTTGIFPGDGSGKQETRAGVVHGAIGGAGVTALL ALCLCLIFFIVKTHRRKAARTAVGRNDTHPTTGSASPKHQKKSKLHGP TETSSCSGAAPTVEMDEELHYASLNFHGMNPSKDTSTEYSEVRTQ

CD33-m Transcript Variant 2; No Exon 2, Exon 7A

mRNA. NM_001082618 (italicized = exon 7A)) AUGCCGCUGCUGCUACUGCUGCCCCUGCUGUGGGCAGACUUGACCCAC AGGCCCAAAAUCCUCAUCCCUGGCACUCUAGAACCCGGCCACUCCAAA AACCUGACCUGCUCUGUGUCCUGGGCCUGUGAGCAGGGAACACCCCCG AUCUUCUCCUGGUUGUCAGCUGCCCCCACCUCCCUGGGCCCCAGGACU ACUCACUCCUCGGUGCUCAUAAUCACCCCACGGCCCCAGGACCACGGC ACCAACCUGACCUGUCAGGUGAAGUUCGCUGGAGCUGGUGUGACUACG GAGAGAACCAUCCAGCUCAACGUCACCUAUGUUCCACAGAACCCAACA ACUGGUAUCUUUCCAGGAGAUGGCUCAGGGAAACAAGAGACCAGAGCA GGAGUGGUUCAUGGGGCCAUUGGAGGAGCUGGUGUUACAGCCCUGCUC GCUCUUUGUCUCUGCCUCAUCUUCUUCAUAGUGAAGACCCACAGGAGG AAAGCAGCCAGGACAGCAGUGGGCAGGAAUGACACCCACCCUACCACA GGGUCAGCCUCCCCGAAACACCAGAAGAAGUCCAAGUUACAUGGCCCC ACUGAAACCUCAAGCUGUUCAGGUGCCGCCCCUACUGUGGAGAUGGAU GAGGAGCUGCAUUAUGCUUCCCUCAACUUUCAUGGGAUGAAUCCUUCC AAGGACACCUCCACCGAAUACUCAGAGGUCAGGACCCAGUGA CD33M-7B: Amino Acid (underlined = exon 2; italicized = exon 7B; SEQ = ID NO: 57) MPLLLLLPLLWAGALAMDPNFWLQVQESVTVQEGLCVLVPCTFFHPIP YYDKNSPVHGYWFREGAIISRDSPVATNKLDQEVQEETQGRFRLLGDP SRNNCSLSIVDARRRDNGSYFFRMERGSTKYSYKSPQLSVHVTDLTHR PKILIPGTLEPGHSKNLTCSVSWACEQGTPPIFSWLSAAPTSLGPRTT HSSVLIITPRPQDHGTNLTCQVKFAGAGVTTERTIQLNVTYVPQNPTT GIFPGDGSGKQETRAGVVHGAIGGAGVTALLALCLCLIFFIVKTHRRK AARTAVGRNDTHPTTGSASPVR

CD33 Transcript Variant 3; Exon 7B

mRNA. NM_001177608 (underlined = exon 2; italicized = exon 7B)) AUGCCGCUGCUGCUACUGCUGCCCCUGCUGUGGGCAGGGGCCCUGGCU AUGGAUCCAAAUUUCUGGCUGCAAGUGCAGGAGUCAGUGACGGUACAG GAGGGUUUGUGCGUCCUCGUGCCCUGCACUUUCUUCCAUCCCAUACCC UACUACGACAAGAACUCCCCAGUUCAUGGUUACUGGUUCCGGGAAGGA GCCAUUAUAUCCAGGGACUCUCCAGUGGCCACAAACAAGCUAGAUCAA GAAGUACAGGAGGAGACUCAGGGCAGAUUCCGCCUCCUUGGGGAUCCC AGUAGGAACAACUGCUCCCUGAGCAUCGUAGACGCCAGGAGGAGGGAU AAUGGUUCAUACUUCUUUCGGAUGGAGAGAGGAAGUACCAAAUACAGU UACAAAUCUCCCCAGCUCUCUGUGCAUGUGACAGACUUGACCCACAGG CCCAAAAUCCUCAUCCCUGGCACUCUAGAACCCGGCCACUCCAAAAAC CUGACCUGCUCUGUGUCCUGGCCUGUGAGCAGGGAACACCCCCGAUCU UCUCCGGUUGUCAGCUGCCCCCACCUCCCUGGGCCCCAGGACUACUCA CUCCUCGGUGCUCAUAAUCACCCCACGGCCCCAGGACCACGGCACCAA CCUGACCUGUCAGGUGAAGUUCGCUGGAGCUGGUGUGACUACGGAGAG AACCAUCCAGCUCAACGUCACCUAUGUUCCACAGAACCCAACAACUGG UAUCUUUCCGGAGAUGGCUCAGGGAAACAAGAGACCAGAGCAGGAGUG GUUCAUGGGGCCAUUGGAGGAGCUGGUGUUACAGCCCUGCUCGCUCUU UGUCUCUGCCUCAUCUUCUUCAUAGUGAAGACCCACAGGAGGAAAGCA GCCAGGACAGCAGUGGGCAGGAAUGACACCCACCCUACCACAGGGUCA GCCUCCCCGGUACGUUGA CD33m-7B Amino Acid (italicized = exon 7B; SEQ ID NO: 58) MPLLLLLPLLWADLTHRPKILIPGTLEPGHSKNLTCSVSWACEQGTPP IFSWLSAAPTSLGPRTTHSSVLIITPRPQDHGTNLTCQVKFAGAGVTT ERTIQLNVTYVPQNPTTGIFPGDGSGKQETRAGVVHGAIGGAGVTALL ALCLCLIFFIVKTHRRKAARTAVGRNDTHPTTGSASPVR

CD33 Tranript Variant 4; No Exon 2, Exon 7B.

mRNA (itaiicized = exon 7B) AUGCCGCUGCUGCUACUGCUGCCCCUGCUGUGGGCAAGGAACAACUGCUC CCUGAGCAUCGUAGACGCCAGGAGGAGGGAUAAUGGUUCAUACUUCUUUC GGAUGGAGAGAGGAAGUACCAAAUACAGUUACAAAUCUCCCCAGCUCUCU GUGCAUGUGACAGACUUGACCCACAGGCCCAAAAUCCUCAUCCCUGGCAC UCUAGAACCCGGCCACUCCAAAAACCUGACCUGCUCUGUGUCCUGGCCUG UGAGCAGGGAACACCCCCGAUCUUCUCCGGUUGUCAGCUGCCCCCACCUC CCUGGGCCCCAGGACUACUCACUCCUCGGUGCUCAUAAUCACCCCACGGC CCCAGGACCACGGCACCAACCUGACCUGUCAGGUGAAGUUCGCUGGAGCU GGUGUGACUACGGAGAGAACCAUCCAGCUCAACGUCACCUAUGUUCCACA GAACCCAACAACUGGUAUCUUUCCGGAGAUGGCUCAGGGAAACAAGAGAC CAGAGCAGGAGUGGUUCAUGGGGCCAUUGGAGGAGCUGGUGUUACAGCCC UGCUCGCUCUUUGUCUCUGCCUCAUCUUCUUCAUAGUGAAGACCCACAGG AGGAAAGCAGCCAGGACAGCAGUGGGCAGGAAUGACACCCACCCUACCAC AGGGUCAGCCUCCCCGGUACGUUGA

Using human CD33 as an exemplary lineage-specific cell-surface protein, regions of the protein in which mutation and/or deletion of amino acids are less likely to result in deleterious effects (e.g., a reduction or abrogation of function) were predicted using PROVEAN software (see: provean.jcvi.org; Choi et al. PLoS ONE (2012) 7(10): e46688). Examples of the predicted regions are shown in boxes in FIG. 2 and exemplary deletions in the predicated regions are presented in Table 2. Numbering of the amino acid residues is based on the amino acid sequence of human CD33 provided by SEQ ID NO: 1 (CD33M-7A).

TABLE 2 Exemplary deletions in CD33 Epitope targeted by Deletion PROVEAN Score cytotoxic agent S248-E252 −5.508 SGKQE (SEQ ID NO: 8) I47-D51 −5.661 IPYYD (SEQ ID NO: 9) G249-T253 −7.078 GKQET (SEQ ID NO: 10) K250-R254 −7.184 KQETR (SEQ ID NO: 11) P48-K52 −7.239 PYYDK (SEQ ID NO: 12) Q251-A255 −7.888 QETRA (SEQ ID NO: 13)

The nucleotide sequence encoding CD33 are genetically manipulated to delete any epitope of the protein (of the extracellular portion of CD33), or a fragment containing such, using conventional methods of nucleic acid manipulation. The amino acid sequences provided below are exemplary sequences of CD33 mutants that have been manipulated to lack each of the epitopes in Table 2.

The amino acid sequence of the extracellular portion of CD33 is provided by SEQ ID NO: 1. The signal peptide is shown in italics and sites for manipulation are shown in underline and boldface. The transmembrane domain is shown in italics with underline.

(SEQ ID NO: 1) MPLLLLLPLL WAGALAMDPN FWLQVQESVT VQEGLCVLVP CTF FHPIPYY DKNS PVHGYW FREGAIISRD SPVATNKLDQ EVQEETQGRF RLLGDPSRNN CSLSIVDARR RDNGSYFFRM ERGSTKYSYK SPQLSVHVTD LTHRPKILIP GTLEPGHSKN LTCSVSWACE QGTPPIFSWL SAAPTSLGPR TTHSSVLIIT PRPQDHGTNL TCQVKFAGAG VTTERTIQLN VTYVPQNPTT GIF PGDGSGK QETRAG VVH G AIGGAGVTAL LALCLCLIFF IV KTHRRKAA RTAVGRNDTH PTTGSASPKH QKKSKIHGPT ETSSCSGAAP TVEMDEELHY ASLNFHGMNP SKDTSTEYSE VRTQ

The amino acid sequence of the extracellular portion of CD33 comprising a deletion of residues S248 through E252 is provided by SEQ ID NO: 2. The signal peptide is shown in italics and the transmembrane domain is shown in italics with underline.

S248_E252insdelTARND; PROVEAN Score=−1.916

(SEQ ID NO: 2) MPLLLLLPLL WAGALAMDPN FWLQVQESVT VQEGLCVLVP CTFFHPIPYY DKNSPVHGYW FREGAIISRD SPVATNKLDQ EVQEETQGRF RLLGDPSRNN CSLSIVDARR RDNGSYFFPM ERGSTKYSYK SPQLSVHVTD LTHRPKILIP GTLEPGHSKN LTCSVSWACE QGTPPIFSWL SAAPTSLGPR TTHSSVLIIT PRPQDHGTNL TCQVKFAGAG VTTERTIQLN VTYVPQNTTT GIFPGDGTAR NDTRAGVVH G   AIGGAGVTAL LALCLCLIFF IV KTHRRKAA RTAVGRNDTH PTTGSASPKH QKKSKLHGPT ETSSCSGAAP TVEMDEELHY ASLNFHGMNT SKDTSTEYSE VRTQ

The amino acid sequence of the extracellular portion of CD33 comprising a deletion of residues 147 through D51 is provided by SEQ ID NO: 3. The signal peptide is shown in italics and the transmembrane domain is shown in italics with underline.

I47_D51insdelVPFFE; PROVEAN Score=−1.672

(SEQ ID NO: 3) MPLLLLLPLL WAGALAMDPN FWLQVQESVT VQEGLCVLVP CTFFHTVPFF EKNSPVHGYW FREGAIISRD SPVATNKLDQ EVQEETQGRF RLLGDPSRNN CSLSIVDARR RDNGSYFFRM ERGSTKYSYK SPQLSVHVTD LTHRPKILIP GTLEPGHSKN LTCSVSWACE QGTPPIFSWL SAAPTSLGPR TTHSSVLIIT PRPQDHGTNL TCQVKFAGAG VTTERTIQLN VTYVPQNPTT GIFPGDGTAR NDTRAGVVH G   AIGGAGVTAL   LALCLCLIFF IV KTHRRKAA RTAVGRNDTH PTTGSASPKH QKKSKLHGPT ETSSCSGAAP TVEMDEELHY ASLNFHGMNP SKDTSTEYSE VRTQ

The amino acid sequence of the extracellular portion of CD33 comprising a deletion of residues G249 through T253 is provided by SEQ ID NO: 4. The signal peptide is shown in italics and the transmembrane domain is shown in italics with underline.

(SEQ ID NO: 4) MPLLLLLPLL WAGALAMDPN FWLQVQESVT VQEGLCVLVP CTFFHPIPYY DKNSPVHGYW FREGAIISRD SPVATNKLDQ EVQEETQGRF RLLGDPSRNN CSLSIVDARR RDNGSYFFRM ERGSTKYSYK SPQLSVHVTD LTHRPKILIP GTLEPGHSKN LTCSVSWACE QGTPPIFSWL SAAPTSLGPR TTHSSVLIIT PRPQDHGTNL TCQVKFAGAG VTTERTIQLN VTYVPQNPTT GIFPGDGSGA GVVH GAIGGA GVTALLALCL CLIFFIV KTH RRKAARTAVG RNDTHPTTGS ASPKHQKKSK LHGPTETSSC SGAAPTVEMD EELHYASLNF HGMNPSKDTS TEYSEVRTQ

The amino acid sequence of the extracellular portion of CD33 comprising a deletion of residues K250 through R254 is provided by SEQ ID NO: 5. The signal peptide is shown in italics and the transmembrane domain is shown in italics with underline.

(SEQ ID NO: 5) MPLLLLLPLL WAGALAMDPN FWLQVQESVT VQEGLCVLVP CTFFHPIPYY DKNSPVHGYW FREGAIISRD SPVATNKLDQ EVQEETQGRF RLLGDPSRNN CSLSIVDARR RDNGSYFFRM ERGSTNYSYK SPQLSVHVTD LTHRPKILIP GTLEPGHSKN LTCSVSWACE QGTPPIFSWL SAAPTSLGPR TTHSSVLIIT PRPQDHGTNL TCQVKFAGAG VTTERTIQLN VTYVPQNPTT GIFPGDGSGA GVVH GAIGGA GVTALLALCL CLIFFIV KTH RRKAARTAVG RNDTHPTTGS ASPKHQKKSK LHGPTETSSC SGAAPTVEMD EELHYASLNF HGMNPSKDTS TEYSEVRTQ

The amino acid sequence of the extracellular portion of CD33 comprising a deletion of residues P48 through K52 is provided by SEQ ID NO: 6. The signal peptide is shown in italics and the transmembrane domain is shown in italics with underline.

(SEQ ID NO: 6) MPLLLLLPLL WAGALAMDPN FWLQVQESVT VQEGLCVLVP CTFFHPINSP VHGYWFREGA IISRDSPVAT NKLDQEVQEE TQGRFRLLGD PSRNNCSLSI VDARRRDNGS YFFRMERGST KYSYKSPQLS VHVTDLTHRP KILIPGTLEP GHSKNLTCSV SWACEQGTPP IFSWLSAAPT SLGPRTTHSS VLIITPRPQD HGTNLTCQVK FAGAGVTTER TIQLNVTYVP QNPTTGIFPG DGSGKQETRA GVVH GAIGGA   GVTALLALCL   CLIFFIV KTH RRKAARTAVG RNDTHPTTGS ASPKHQKKSK LHGPTETSSC SGAAPTVEMD EELHYASLNF HGMNPSKDTS TEYSEVRTQ

The amino acid sequence of the extracellular portion of CD33 comprising a deletion of residues Q251 through A255 is provided by SEQ ID NO: 7. The signal peptide is shown in italics and the transmembrane domain is shown in italics with underline.

(SEQ ID NO: 7) MPLLLLLPLL WAGALAMDPN FWLQVQESVT VQEGLCVLVP CTFFHPIPYY DKNSPVHGYW FREGAIISRD SPVATNKLDQ EVQEETQGRF RLLGDPSRNN CSLSIVDARR RDNGSYFFRM ERGSTKYSYK SPQLSVHVTD LTHRPKILIP GTLEPGHSKN LTCSVSWACE QGTPPIFSWL SAAPTSLGPR TTHSSVLIIT PRPQDHGTNL TCQVKFAGAG VTTERTIQLN VTYVPQNPTT GIFPGDGSGK GVVH GAIGGA GVTALLALCL CLIFFIV KTH RRKAARTAVG RNDTHPTTGS ASPKHQKKSK LHGPTETSSC SGAAPTVEMD EELHYASLNF HGMNPSKDTS TEYSEVRTQ

In some examples, provided herein are variants of CD33, which may comprise a deletion or mutation of a fragment of the protein that is encoded by any one of the exons of CD33, or a deletion or mutation in a non-essential epitope. The predicted structure of CD33 includes two immunoglobulin domains, an IgV domain and an IgC2 domain. In some embodiments, a portion of the immunoglobulin V domain of CD33 is deleted or mutated. In some embodiments, a portion of the immunoglobulin C domain of CD33 is deleted or mutated. In some embodiments, exon 2 of CD33 is deleted or mutated. In some embodiments, the CD33 variant lacks amino acid residues W11 to T139 of SEQ ID NO: 1. In some embodiments, the CD33 variant lacks amino acid residues G13 to T139 of SEQ ID NO: 1. In some embodiments, the deleted or mutated fragment overlaps or encompasses the epitope to which the cytotoxic agent binds. As described in Example 1, in some embodiments, the epitope comprises amino acids 47-51 or 248-252 of the extracellular portion of CD33 (SEQ ID NO: 1). In some embodiments, the epitope comprises amino acids 248-252 (SEQ ID NO: 8), 47-51 (SEQ ID NO: 9), 249-253 (SEQ ID NO: 10), 250-254 (SEQ ID NO: 11), 48-52 (SEQ ID NO: 12), or 251-255 (SEQ ID NO: 13) of the extracellular portion of CD33 (SEQ ID NO: 1).

In some embodiments, the genetically engineered hematopoietic stem cells have genetic edits in a CD33 gene, wherein exon2 of CD33 is mutated or deleted. In some embodiments, exon 2 of CD33 is mutated or deleted (see the amino acid sequence of the exon 2-encoded fragment above). In some embodiments, the genetically engineered hematopoietic stem cells have genetic edits in a CD33 gene resulting in expression of CD33 with deleted or mutated exon 2 of CD33. In some embodiments, genetically engineered hematopoietic stem cells express CD33, in which exon 2 of CD33 is mutated or deleted. In some examples, the genetically engineered hematopoietic cells have a genetically engineered CD33 gene (e.g., a genetically engineered endogenous CD33 gene), wherein the engineering results in expression of a CD33 variant having the fragment encoded by exon 2 deleted (CD33ex2).

In some embodiments, the CD33 genes edited HSCs expressing CD33 variant having the fragment encoded by exon 2 deleted also comprise a partial or complete deletion in the adjacent introns (intron 1 and intron 2) in addition to the deletion of exon 2.

Exemplary amino acid sequence of CD33 mutants, with fragments G13-T139 deleted, is provided below (the junction of exon 1-encoded fragment and exon-3 encoded fragment is shown in boldface):

(SEQ ID NO: 56) MPLLLLLPLLWADLTHRPKILIPGTLEPGHSKNLTCSVSWACEQGTPPIF SWLSAAPTSLGPRTTHSSVLIITPRPQDHGTNLTCQVKFAGAGVTTERTI QLNVTYVPQNPTTGIFPGDGSGKQETRAGVVHGAIGGAGVTALLALCLCL IFFIVKTHRRKLARTAVGRNDTHPTTGSASPKHQKKSKLHGPTETSSCSG AAPTVEMDEELHYASLNFHGMNPSKDTSTEYSEVRTQ (SEQ ID NO: 58) MPLLLLLPLLWADLTHRPKILIPGTLEPGHSKNLTCSVSWACEQGTPPIF SWLSAAPTSLGPRTTHSSVLIITPRPQDHGTNLTCQVKFAGAGVTTERTI QLNVTYVPQNPTTGIFPGDGSGKQETRAGVVHGAIGGAGVTALLALCLCL IFFIVKTHRRKAARTAVGRNDTHPTTGSASPVR

While certain cells may express CD33 proteins lacking the fragment encoded by exon 2, the genetically engineered hematopoietic cells are different from such native cells in at least the aspect that these cells have undergone genome editing to modify a CD33 gene such as an endogenous CD33 gene. In other words, the parent hematopoietic stem cells for producing the genetically engineered HSCs carry a CD33 gene that produces exon 2-containing transcripts.

Genetically engineered hematopoietic stem cells carrying an edited CD33 gene that expresses this CD33 mutant are also within the scope of the present disclosure. Such cells may be a homogenous population containing cells expressing the same CD33 mutant (e.g., CD33ex2). Alternatively, the cells may be a heterogeneous population containing cells expressing different CD33 mutants (which may due to heterogeneous editing/repairing events inside cells) or cells that do not express CD33 (CD33KO). In specific examples, the genetically engineered HSCs may be a heterogeneous population containing cells expressing CD33ex2 and cells that do not express CD33 (CD33KO).

Genetically engineered hematopoietic stem cells having edited a CD33 gene can be prepared by a suitable genome editing method, such as those known in the art or disclosed herein. In some embodiments, the genetically engineered hematopoietic stem cells described herein can be generated using the CRISPR approach. See discussions herein. In certain examples, specific guide RNAs targeting a fragment of the CD33 gene (an exon sequence or an intron sequence) can be used in the CRISPR method. Exemplary gRNAs for editing the CD33 gene (e.g., deletion of exon 2) are provided in Example 2, Table 4, and Example 3 below.

In some examples, multiple gRNAs can be used for editing the CD33 gene via CRISPR Different combinations of gRNAs, e.g., selected from those listed in Table 4, can be used in the multiplex approach.

A CD33 pseudogene, known as SIGLEC22P (Gene ID 114195), is located upstream of the CD33 gene and shares a certain degree of sequence homology with the CD33 gene. gRNAs that cross-target regions in the pseudogene and regions in the CD33 gene may lead to production of aberrant gene products. Thus, in some embodiments, the gRNAs used in methods of editing CD33 via CRISPR preferably have low or no cross-reactivity with regions inside the pseudogene. In some instances, the gRNAs used in methods of editing CD33 via CRISPR preferably have low or no cross-reactivity with region(s) in Exon 1, intron 1 or Exon 2 of CD33 that are homologous to the pseudogene. Such gRNAs can be designed by comparing the sequences of the pseudogene and the CD33 gene to choose targeting sites inside the CD33 gene that have less or no homology to regions of the pseudogene.

In one example, the pair of gRNA 18 (TTCATGGGTACTGCAGGGCA; SEQ ID NO: 44)) and gRNA 24 (GTGAGTGGCTGTGGGGAGAG: SEQ ID NO: 50) are used for editing CD33 via CRISPR. Also provided herein are methods of genetically editing CD33 in hematopoietic cells (e.g., HSCs) via CRISPR using one or more of the gRNAs described herein, for example, the pair of gRNA18+gRNA24. As described herein, the length of a gRNA sequence may be modified (increased or decreased), for example, to enhance editing specificity and/or efficiency. In some embodiments, the length of gRNA 24 is 20 base pairs. In some embodiments, reducing the length of gRNA 24 may reduce the editing efficiency of gRNA 24 for CD33.

Because of the mechanism of Cas9 cutting and DNA repair, there will be a spectrum of repair events including small insertions on 1-2 nucleotides and occasionally longer deletions. Representative sequences of repaired CD33exon 2 deletion products (intron 1-intron 2 displayed) are shown below (SEQ ID NOs:59-65):

Example Repair Sequence Length Comment 1.  Ligation: CCCTGCTGTGGGCAGgtgagtggctgtggggagcagggctgggatgggaccct 0 2.  Insertion: CCCTGCTGTGGGCAGgtgaAtggctgCggggagcagggctgggatgggaccc +1 3.  Insertion: CCCTGCTGTGGGCAGgtgagtggctgtgggcaggtgagtggctgggatgggaccct +6/−3 4.  Insertion: CCCTGCTGTGGGCAGgtgaAtggctgCggggTactgcagggcagggctgggatgggaccct +8 5.  Deletion: CCCTGCTGTGGGCAGgtgaAt-------------ggctggatgggaccct +1/−14 6.  Deletion: CCCTGCTGTGGGCAGgtgaatggctg----cagggctgggatgggaccct −7 7.  Deletion: CCCTGCTGTGGG-----------------------ctgggatgggaccct −2 −3nt in exon 1 Despite the heterogeneity at the genomic DNA level, the RNA transcripts provided from the edited CD33 gene all encode CD33 mutants having the fragment encoded by exon 2 deleted.

(iii) Genetically Engineered Hematopoietic Cells Expressing Both CD19 and CD33 Mutants

Also provided herein are a genetically engineered hematopoietic cells such as HSCs that have both the CD19 and CD33 genes edited. In some embodiments, provide herein is a population of genetically engineered hematopoietic HSCs in which at least 50% of the cells carry genetically edited CD19 and CD33 cells in at least on chromosome.

In some embodiments, the edited CD19 gene is capable of expressing a CD19 mutant having the fragment encoded by exon 2 deleted. Alternatively or in addition, the edited CD33 gene is capable of expressing a CD33 mutant having the fragment encoded by exon 3 deleted.

The genetically engineered hematopoietic cells having both CD19 and CD33 genes edited can be prepared by conventional methods. In some embodiments, such cells are prepared by CRISPR using a pair of gRNAs, one targeting CD19 and the other targeting CD33. Examples are provided in Example 3. Table 8 below. In one example, the pair of gRNAs can be introduced into parent HSCs simultaneously and cells having genetic edits in CD19 and/or CD33 can be harvested for further use.

Masked Lineage-Specific Cell Surface Antigens

While many of the embodiments described herein involve mutations to the endogenous genes encoding lineage-specific cell surface antigens, it is understood that other approaches may be used instead of or in addition to mutation. For instance, a lineage-specific cell surface antigen can be masked, e.g., to prevent or reduce its recognition by an immunotherapeutic agent. In some embodiments, masking is used on a lineage-specific cell surface antigen that is difficult to mutate, e.g., because mutation of the gene is inefficient or is deleterious to cells expressing the mutant. In some embodiments, the lineage-specific cell surface protein is CD45. In some embodiments, masking is performed on a cell type described herein, e.g., an HSC or HPC.

In some embodiments, masking is accomplished by expressing a masking protein in the cell of interest (e.g., by stably expressing DNA encoding the masking protein in the cell). In some embodiments, the masking protein comprises a binding domain (e.g., an antibody or antigen-binding fragment, e.g., an scFv) that binds the lineage-specific cell surface protein, e.g., in a way that reduces binding of an immunotherapeutic agent to the lineage-specific cell surface protein, e.g., by competing for binding at the same epitope. In some embodiments, the binding domain binds CD45. In some embodiments, the making protein further comprises one or more sequences that direct its localization to the surface of the cell. In some embodiments, the masking protein comprises a transmembrane domain fused to the binding domain. The masking protein may comprise a linker disposed between the transmembrane domain and the binding domain. The masking protein may be expressed at a level that binds to a sufficient amount of the lineage-specific cells surface antigen that an immunotherapeutic agent displays reduced binding to and/or reduced killing of a cell expressing the masking protein compared to an otherwise similar cell that does not express the masking protein.

In some embodiments, a cell described herein has reduced binding to (and/or reduced killing by) two different immunotherapeutic agents that recognize two different lineage-specific cell surface antigens. For instance, the cell may have a mutation at a gene encoding a first lineage-specific cell surface antigen, and may comprise a masking protein that masks a second lineage-specific cell surface antigen. In some embodiments, the cell may comprise a first masking protein that masks a first lineage-specific cell surface antigen and a second masking protein that masks a second lineage-specific cell surface antigen. In some embodiments, the first and second lineage-specific cell surface antigens are antigens listed in Table 1A.

Cells Altered at One or More Lineage-Specific Cell Surface Antigens

While many of the embodiments described herein involve two or more lineage-specific cell surface antigens, the application also discloses various cells altered with respect to a single lineage-specific cell surface antigen. For instance, the disclosure describes cells mutated at any one of the lineage-specific cell surface antigens described herein (e.g., mutated at one or both alleles of the lineage-specific cell surface antigen). The disclosure also describes cells expressing a single masking protein for a single lineage-specific cell surface antigen.

II. Cytotoxic Agents Specific to Lineage-Specific Cell-Surface Antigens

Cytotoxic agents targeting cells (e.g., cancer cells) expressing a lineage-specific cell-surface antigen can be co-used with the genetically engineered hematopoietic cells as described herein. As used herein, the term “cytotoxic agent” refers to any agent that can directly or indirectly induce cytotoxicity of a target cell, which expresses the lineage-specific cell-surface antigen (e.g., a target cancer cell). Such a cytotoxic agent may comprise a protein-binding fragment that binds and targets an epitope of the lineage-specific cell-surface antigen. In some instances, the cytotoxic agent may comprise an antibody, which may be conjugated to a drug (e.g., an anti-cancer drug) to form an antibody-drug conjugate (ADC).

The cytotoxic agent for use in the methods described herein may directly cause cell death of a target cell. For example, the cytotoxic agent can be an immune cell (e.g., a cytotoxic T cell) expressing a chimeric receptor. Upon engagement of the protein binding domain of the chimeric receptor with the corresponding epitope in a lineage-specific cell-surface antigen, a signal (e.g., activation signal) may be transduced to the immune cell resulting in release of cytotoxic molecules, such as peroforins and granzymes, as well as activation of effector functions, leading to death of the target cell. In another example, the cytotoxic agent may be an ADC molecule. Upon binding to a target cell, the drug moiety in the ADC would exert cytotoxic activity, leading to target cell death.

In other embodiments, the cytotoxic agent may indirectly induce cell death of the target cell. For example, the cytotoxic agent may be an antibody, which, upon binding to the target cell, would trigger effector activities (e.g., ADCC) and/or recruit other factors (e.g., complements), resulting in target cell death.

Any of the cytotoxic agents described herein target a lineage-specific cell-surface antigen, e.g., comprising a protein-binding fragment that specifically binds an epitope in the lineage-specific protein.

For leukemias that become resistance to CAR-T therapy, an emerging strategy is to simultaneously target alternative or multiple antigens (see e.g., Nature Reviews Immunology (2019), Volume 19, pages 73-74 and Cancer Discov. (2018) October; 8(10):1219-1226).

In some embodiments, more than one (e.g., 2, 3, 4, 5 or more) cytotoxic agent is used to target more than one (e.g., 1, 2, 3, 4, 5 or more) epitopes of a lineage-specific cell-surface antigen. In some embodiments, more than one (e.g., 1, 2, 3, 4, 5 or more) cytotoxic agent is used to target an epitope(s) of one or more lineage-specific cell-surface antigen(s) (e.g., additional/alternative antigens). In some embodiments, targeting of more than one lineage-specific cell-surface antigen reduces relapse of a hematopoietic malignancy. In one embodiment, two or more cytotoxic agents are used in the methods described herein. In some embodiments, the two or more cytotoxic agents are administered concurrently. In some embodiments, the two or more cytotoxic agents are administered sequentially.

Examples of additional cell-surface proteins that may be targeted are known in the art (see, e.g., Tasian, Ther. Adv. Hematol. (2018) 9(6): 135-148: Hoseini and Cheung, Blood Cancer Journal (2017) 7, e522; doi:10.1038/bcj.2017.2; Taraseviciute et al. Hematology and Oncology (2019) 31(1)). In some embodiments, the methods described herein involve targeting a lineage-specific cell-surface antigen and one or more additional cell-surface proteins. In some embodiments, the methods described herein involved administering a cytotoxic agent targeting CD33 and at least one additional cytotoxic agent that targets an additional cell-surface protein, such as CD7, CD13, CD15, CD25 (IL-2Rα), CD30, CD32 (FcγRIII), CD38, CD44v6, CD45, CD47, CD56, CD90 (Thy 1), CD96, CD117 (c-KIT), CD123 (IL3Ra), CD135 (FLT3R), CD174 (Lewis-Y), CLL-1 (CLEC12A), folate receptor-b, IL1RAP, MUC1, NKG2D/NKG2DL, TIM-3 (HAVCR2), CD19, and WT1. In some embodiments, the methods described herein involved administering a cytotoxic agent targeting CD19 and at least one additional cytotoxic agent that targets an additional cell-surface protein, such as CD7, CD13, CD15, CD25 (IL-2Rα), CD30, CD32 (FcγRIII), CD38, CD44v6, CD45, CD47, CD56, CD90 (Thy1), CD96, CD117 (c-KIT), CD123 (IL3Rα), CD135 (FLT3R), CD174 (Lewis-Y), CLL-1 (CLEC12A), folate receptor-b, IL1RAP, MUC1, NKG2D/NKG2DL, TIM-3 (HAVCR2), CD19, and WT1.

In some examples, a cytotoxic agent is used to target CD33 and a second cytotoxic agent is used to target CD19. In some examples, a cytotoxic agent is used to target CD33 and a second cytotoxic agent is used to target an additional cell-surface protein. In some examples, a cytotoxic agent is used to target CD19 and a second cytotoxic agent is used to target an additional cell-surface protein. In some examples, a cytotoxic agent is used to target CD33 and a second cytotoxic agent is used to target CD13. In some examples, a cytotoxic agent is used to target CD33 and a second cytotoxic agent is used to target CD13. In some examples, a cytotoxic agent is used to target CD33 and a second cytotoxic agent is used to target CD123. In some examples, a cytotoxic agent is used to target CD19 and a second cytotoxic agent is used to target CD13. In some examples, a cytotoxic agent is used to target CD19 and a second cytotoxic agent is used to target CD123. In some examples, a cytotoxic agent is used to target CD13 and a second cytotoxic agent is used to target CD123.

In some examples, a cytotoxic agent is used to target CD33, a second cytotoxic agent is used to target CD19, and a third cytotoxic agent is used to target CD13. In some examples, a cytotoxic agent is used to target CD33, a second cytotoxic agent is used to target CD19, and a third cytotoxic agent is used to target CD123. In some examples, a cytotoxic agent is used to target CD33, a second cytotoxic agent is used to target CD13, and a third cytotoxic agent is used to target CD123. In some examples, a cytotoxic agent is used to target CD19, a second cytotoxic agent is used to target CD19, and a third cytotoxic agent is used to target CD13. In some examples, a cytotoxic agent is used to target CD33, a second cytotoxic agent is used to target CD19, a third cytotoxic agent is used to target CD13, and fourth cytotoxic agent used to target CD123.

(i) Therapeutic Antibodies

Any antibody or an antigen-binding fragment thereof can be used as a cytotoxic agent or for constructing a cytotoxic agent that targets an epitope of a lineage-specific cell-surface antigen, as described herein. Such an antibody or antigen-binding fragment can be prepared by a conventional method, for example, the hybridoma technology or recombinant technology.

As used herein, the term “antibody” refers to a glycoprotein comprising at least two heavy (H) chains and two light (L) chains inter-connected by disulfide bonds, i.e., covalent heterotetramers comprised of two identical Ig H chains and two identical L chains that are encoded by different genes. Each heavy chain is comprised of a heavy chain variable region (abbreviated herein as HCVR or VH) and a heavy chain constant region. The heavy chain constant region is comprised of three domains, CH1, CH2 and CH3. Each light chain is comprised of a light chain variable region (abbreviated herein as LCVR or VL) and a light chain constant region. The light chain constant region is comprised of one domain, CL. The VH and VL regions can be further subdivided into regions of hypervariability, termed complementarity determining regions (CDR), interspersed with regions that are more conserved, termed framework regions (FR). Each VH and VL is composed of three CDRs and four FRs, arranged from amino-terminus to carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. The variable regions of the heavy and light chains contain a binding domain that interacts with an antigen. The constant regions of the antibodies may mediate the binding of the immunoglobulin to host tissues or factors, including various cells of the immune system (e.g., effector cells) and the first component (Clq) of the classical complement system. Formation of a mature functional antibody molecule can be accomplished when two proteins are expressed in stoichiometric quantities and self-assemble with the proper configuration.

In some embodiments, the antigen-binding fragment is a single-chain antibody fragment (scFv) that specifically binds the epitope of the lineage-specific cell-surface antigen. In other embodiments, the antigen-binding fragment is a full-length antibody that specifically binds the epitope of the lineage-specific cell-surface antigen.

As described herein and as will be evident to a skilled artisan, the CDRs of an antibody specifically bind to the epitope of a target protein/antigen (the lineage-specific cell-surface protein/antigen).

In some embodiments, the antibodies are full-length antibodies, meaning the antibodies comprise a fragment crystallizable (Fc) portion and a fragment antigen-binding (Fab) portion. In some embodiments, the antibodies are of the isotype IgG, IgA, IgM, IgA, or IgD. In some embodiments, a population of antibodies comprises one isotype of antibody. In some embodiments, the antibodies are IgG antibodies. In some embodiments, the antibodies are IgM antibodies. In some embodiments, a population of antibodies comprises more than one isotype of antibody. In some embodiments, a population of antibodies is comprised of a majority of one isotype of antibodies but also contains one or more other isotypes of antibodies. In some embodiments, the antibodies are selected from the group consisting of IgG1, IgG2, IgG3, IgG4, IgM, IgA1, IgA2, IgAsec, IgD, IgE.

The antibodies described herein may specifically bind to a target protein. As used herein, “specific binding” refers to antibody binding to a predetermined protein, such as a cancer antigen. “Specific binding” involves more frequent, more rapid, greater duration of interaction, and/or greater affinity to a target protein relative to alternative proteins. In some embodiments, a population of antibodies specifically binds to a particular epitope of a target protein, meaning the antibodies bind to the particular protein with more frequently, more rapidly, for greater duration of interaction, and/or with greater affinity to the epitope relative to alternative epitopes of the same target protein or to epitopes of another protein. In some embodiments, the antibodies that specifically bind to a particular epitope of a target protein may not bind to other epitopes of the same protein.

Antibodies may be selected based on the binding affinity of the antibody to the target protein or epitope. Alternatively or in additional, the antibodies may be mutated to introduce one or more mutations to modify (e.g., enhance or reduce) the binding affinity of the antibody to the target protein or epitope.

The present antibodies or antigen-binding portions can specifically bind with a dissociation constant (K_(D)) of less than about 10⁻⁷ M, less than about 10⁻⁸ M, less than about 10⁻⁹ M, less than about 10⁻¹⁰ M, less than about 10⁻¹¹ M, or less than about 10⁻¹² M. Affinities of the antibodies according to the present disclosure can be readily determined using conventional techniques (see, e.g., Scatchard et al., Ann. N.Y. Acad. Sci. (1949) 51:660; and U.S. Pat. Nos. 5,283,173, 5,468,614, or the equivalent).

The binding affinity or binding specificity for an epitope or protein can be determined by a variety of methods including equilibrium dialysis, equilibrium binding, gel filtration, ELISA, surface plasmon resonance, or spectroscopy.

For example, antibodies (of antigen-binding fragments thereof) specific to an epitope of a lineage-specific protein of interest can be made by the conventional hybridoma technology. The lineage-specific protein, which may be coupled to a carrier protein such as KLH, can be used to immunize a host animal for generating antibodies binding to that complex. The route and schedule of immunization of the host animal are generally in keeping with established and conventional techniques for antibody stimulation and production, as further described herein. General techniques for production of mouse, humanized, and human antibodies are known in the art and are described herein. It is contemplated that any mammalian subject including humans or antibody producing cells therefrom can be manipulated to serve as the basis for production of mammalian, including human hybridoma cell lines. Typically, the host animal is inoculated intraperitoneally, intramuscularly, orally, subcutaneously, intraplantar, and/or intradermally with an amount of immunogen, including as described herein.

Hybridomas can be prepared from the lymphocytes and immortalized myeloma cells using the general somatic cell hybridization technique of Kohler, B, and Milstein, C. (1975) Nature 256:495-497 or as modified by Buck, D. W., et al., In Vitro, 18:377-381 (1982). Available myeloma lines, including but not limited to X63-Ag8.653 and those from the Salk Institute, Cell Distribution Center, San Diego. Calif., USA, may be used in the hybridization. Generally, the technique involves fusing myeloma cells and lymphoid cells using a fusogen such as polyethylene glycol, or by electrical means well known to those skilled in the art. After the fusion, the cells are separated from the fusion medium and grown in a selective growth medium, such as hypoxanthine-aminopterin-thymidine (HAT) medium, to eliminate unhybridized parent cells. Any of the media described herein, supplemented with or without serum, can be used for culturing hybridomas that secrete monoclonal antibodies. As another alternative to the cell fusion technique, EBV immortalized B cells may be used to produce the TCR-like monoclonal antibodies described herein. The hybridomas are expanded and subcloned, if desired, and supernatants are assayed for anti-immunogen activity by conventional immunoassay procedures (e.g., radioimmunoassay, enzyme immunoassay, or fluorescence immunoassay).

Hybridomas that may be used as source of antibodies encompass all derivatives, progeny cells of the parent hybridomas that produce monoclonal antibodies capable of binding to a lineage-specific protein. Hybridomas that produce such antibodies may be grown in vitro or in vivo using known procedures. The monoclonal antibodies may be isolated from the culture media or body fluids, by conventional immunoglobulin purification procedures such as ammonium sulfate precipitation, gel electrophoresis, dialysis, chromatography, and ultrafiltration, if desired. Undesired activity if present, can be removed, for example, by running the preparation over adsorbents made of the immunogen attached to a solid phase and eluting or releasing the desired antibodies off the immunogen. Immunization of a host animal with a target protein or a fragment containing the target amino acid sequence conjugated to a protein that is immunogenic in the species to be immunized, e.g., keyhole limpet hemocyanin, serum albumin, bovine thyroglobulin, or soybean trypsin inhibitor using a bifunctional or derivatizing agent, for example maleimidobenzoyl sulfosuccinimide ester (conjugation through cysteine residues), N-hydroxysuccinimide (through lysine residues), glutaraldehyde, succinic anhydride, SOCl, or R1N═C═NR, where R and R1 are different alkyl groups, can yield a population of antibodies (e.g., monoclonal antibodies).

If desired, an antibody of interest (e.g., produced by a hybridoma) may be sequenced and the polynucleotide sequence may then be cloned into a vector for expression or propagation. The sequence encoding the antibody of interest may be maintained in vector in a host cell and the host cell can then be expanded and frozen for future use. In an alternative, the polynucleotide sequence may be used for genetic manipulation to “humanize” the antibody or to improve the affinity (affinity maturation), or other characteristics of the antibody. For example, the constant region may be engineered to more resemble human constant regions to avoid immune response if the antibody is used in clinical trials and treatments in humans. It may be desirable to genetically manipulate the antibody sequence to obtain greater affinity to the lineage-specific protein. In some examples, the antibody sequence is manipulated to increase binding affinity of the antibody to the lineage-specific protein such that lower levels of the lineage-specific protein are detected by the antibody. In some embodiments, antibodies that have increased binding to the lineage-specific protein may be used to reduce or prevent relapse of a hematopoietic malignancy. It will be apparent to one of skill in the art that one or more polynucleotide changes can be made to the antibody and still maintain its binding specificity to the target protein.

In other embodiments, fully human antibodies can be obtained by using commercially available mice that have been engineered to express specific human immunoglobulin proteins. Transgenic animals that are designed to produce a more desirable (e.g., fully human antibodies) or more robust immune response may also be used for generation of humanized or human antibodies. Examples of such technology are Xenomouse® from Amgen, Inc. (Fremont, Calif.) and HuMAb-Mouse® and TC Mouse™ from Medarex, Inc. (Princeton, N.J.). In another alternative, antibodies may be made recombinantly by phage display or yeast technology. See, for example, U.S. Pat. Nos. 5,565,332, 5,580,717; 5,733,743; and 6,265,150: and Winter et al., (1994) Annu. Rev. Immunol. 12:433-455. Alternatively, the phage display technology (McCafferty et al., (1990) Nature 348:552-553) can be used to produce human antibodies and antibody fragments in vitro, from immunoglobulin variable (V) domain gene repertoires from unimmunized donors.

Antigen-binding fragments of an intact antibody (full-length antibody) can be prepared via routine methods. For example, F(ab′)₂ fragments can be produced by pepsin digestion of an antibody molecule, and Fab fragments that can be generated by reducing the disulfide bridges of F(ab′)₂ fragments.

Genetically engineered antibodies, such as humanized antibodies, chimeric antibodies, single-chain antibodies, and bi-specific antibodies, can be produced via, e.g., conventional recombinant technology. In one example, DNA encoding a monoclonal antibodies specific to a target protein can be readily isolated and sequenced using conventional procedures (e.g., by using oligonucleotide probes that are capable of binding specifically to genes encoding the heavy and light chains of the monoclonal antibodies). The hybridoma cells serve as a preferred source of such DNA. Once isolated, the DNA may be placed into one or more expression vectors, which are then transfected into host cells such as E. coli cells, simian COS cells, Chinese hamster ovary (CHO) cells, or myeloma cells that do not otherwise produce immunoglobulin protein, to obtain the synthesis of monoclonal antibodies in the recombinant host cells. See, e.g., PCT Publication No. WO 87/04462. The DNA can then be modified, for example, by substituting the coding sequence for human heavy and light chain constant domains in place of the homologous murine sequences, Morrison et al., (1984) Proc. Nat. Acad. Sci. 81:6851, or by covalently joining to the immunoglobulin coding sequence all or part of the coding sequence for a non-immunoglobulin polypeptide. In that manner, genetically engineered antibodies, such as “chimeric” or “hybrid” antibodies: can be prepared that have the binding specificity of a target protein.

Techniques developed for the production of “chimeric antibodies” are well known in the art. See, e.g., Morrison et al. (1984) Proc. Natl. Acad. Sci. USA 81, 6851; Neuberger et al. (1984) Nature 312, 604; and Takeda et al. (1984) Nature 314:452.

Methods for constructing humanized antibodies are also well known in the art. See, e.g., Queen et al., Proc. Natl. Acad. Sci. USA, 86:10029-10033 (1989). In one example, variable regions of VH and VL of a parent non-human antibody are subjected to three-dimensional molecular modeling analysis following methods known in the art. Next, framework amino acid residues predicted to be important for the formation of the correct CDR structures are identified using the same molecular modeling analysis. In parallel, human VH and VL chains having amino acid sequences that are homologous to those of the parent non-human antibody are identified from any antibody gene database using the parent VH and VL sequences as search queries. Human VH and VL acceptor genes are then selected.

The CDR regions within the selected human acceptor genes can be replaced with the CDR regions from the parent non-human antibody or functional variants thereof. When necessary, residues within the framework regions of the parent chain that are predicted to be important in interacting with the CDR regions (see above description) can be used to substitute for the corresponding residues in the human acceptor genes.

A single-chain antibody can be prepared via recombinant technology by linking a nucleotide sequence coding for a heavy chain variable region and a nucleotide sequence coding for a light chain variable region. Preferably, a flexible linker is incorporated between the two variable regions. Alternatively, techniques described for the production of single chain antibodies (U.S. Pat. Nos. 4,946,778 and 4,704,692) can be adapted to produce a phage or yeast scFv library and scFv clones specific to a lineage-specific protein can be identified from the library following routine procedures. Positive clones can be subjected to further screening to identify those that bind lineage-specific protein.

In some instances, the cytotoxic agent for use in the methods described herein comprises an antigen-binding fragment that targets the lineage-specific protein CD33. In other examples, the cytotoxic agent for use in the methods described herein comprises an antigen-binding fragment that targets the lineage-specific protein CD19. In other example, two or more cytotoxic agents are used in the methods described herein. In some embodiments, the two or more cytotoxic agents are administered concurrently. In some embodiments, the two or more cytotoxic agents are administered sequentially. In one non-limiting example, antibodies and antigen-binding fragments targeting CD33 and CD19 in combination are used in the methods described herein. In one non-limiting example, antibodies and antigen-binding fragments targeting CD33 are used in combination with a cytotoxic agent (e.g., antibodies, immune cells expressing chimeric antigen receptors, antibody-drug conjugates) that targets a second lineage-specific cell-surface antigen or an additional cell-surface protein. In one non-limiting example, antibodies and antigen-binding fragments targeting CD19 are used in combination with a cytotoxic agent (e.g., antibodies, immune cells expressing chimeric antigen receptors, antibody-drug conjugates) that targets a second lineage-specific cell-surface antigen or an additional cell-surface protein.

In some embodiments, bispecific or multi-specific antibodies may be used to target more than one epitope (e.g., more than one epitope of a lineage-specific cell-surface antigen, epitopes of more than one lineage-specific cell-surface antigen, an epitope of lineage-specific cell-surface antigen and an epitope of an additional cell-surface antigen). See, e.g., Hoseini et al. Blood Cancer Journal (2017) 7, e552. Non-limiting examples of bispecific antibodies include tandem double scFv (e.g., single-chain bispecific tandem fragment variable (scBsTaFv), bispecific T-cell engager (BiTE), bispecific single-chain Fv (bsscFv), bispecific killer-cell engager (BiKE), dual-affinity re-targeting (DART), diabody, tandem diabodies (TandAb), single-chain Fv triplebody (sctb), bispecific scFv immunofusion (Blf), Fabsc, dual-variable-domain immunoglobulin (DVD-Ig), CrossMab (CH1-CL), modular bispecific antibody (IgG-scFv). See, e.g., Marin-Acevedo et al. J. Hematol. Oncol. (2018)11: 8; Slaney et al. Cancer Discovery (2018) 8(8): 924-934, and Elgundi et al. Advanced Drug Discovery Reviews (2017) 122: 2-19.

In some embodiments, the antibody is a bispecific T-cell engager (BiTE) comprising two linked scFv molecules. In some embodiments, at least of the linked scFv of the BiTE binds an epitope of a lineage-specific cell-surface protein (e.g., CD33 or CD19). In one example, the BiTE is blinatumomab. See, e.g. Slaney et al. Cancer Discovery (2018) 8(8): 924-934.

For example, an antibody that targets both CD33 and CD19 may be used in the methods described herein. Antibodies and antigen-binding fragments targeting CD33 or CD19 or a combination thereof can be prepared by routine practice. Non-limited examples of antigen-binding fragments that target CD19 can be found in Porter D L et al. NEJM (2011) 365:725-33 and Kalos M et al. Sci Transl Med. (2011) 3:95ra73. See also descriptions herein. Such CD19-targeting antigen-binding fragments can be used for making the CAR constructs described herein.

In some embodiments, a bispecific antibody may be used in which one molecule targets an epitope of a lineage-specific cell-surface protein on a target cell and the other molecule targets a surface antigen on an effector cell (e.g., T cell, NK cell) such that the target cell is brought into proximity with the effector cell. See, e.g., Hoseini et al. Blood Cancer Journal (2017) 7, e552.

In some embodiments, two or more (e.g., 2, 3, 4, 5 or more) epitopes of a lineage-specific cell-surface protein have been modified, enabling two or more (e.g., 2, 3, 4, 5 or more) different cytotoxic agents (e.g., two antibodies) to be targeted to the two or more epitopes. In some embodiments, the antibodies could work synergistically to enhance efficacy. In some embodiments, epitopes of two or more (e.g., 2, 3, 4, 5 or more) lineage-specific cell surface protein have been modified, enabling two or more (e.g., 2, 3, 4, 5 or more) different cytotoxic agents (e.g., two antibodies) to be targeted to epitopes of the two or more lineage-specific cell-surface proteins. In some embodiments, one or more (e.g., 1, 2, 3, 4, 5 or more) epitopes of a lineage-specific cell-surface protein have been modified and one or more (e.g., 1, 2, 3, 4, 5 or more) epitopes of an additional cell-surface protein have been modified, enabling two or more (e.g., 2, 3, 4, 5 or more) different cytotoxic agents (e.g., two antibodies) to be targeted to epitopes of the lineage-specific cell-surface protein and epitopes of additional cell-surface protein. In some embodiments, targeting of two or more lineage-specific cell-surface protein may reduce relapse of a hematopoietic malignancy.

In some embodiments, the methods described herein involve administering a cytotoxic agent that targets an epitope of a lineage-specific cell-surface antigen that is mutated in the population of genetically engineered hematopoietic cells. In some embodiments, the methods described herein involve administering a cytotoxic agent that targets an epitope of a lineage-specific cell-surface antigen that is mutated in the population of genetically engineered hematopoietic cells and one or more additional cytotoxic agents that target one or more additional cell-surface proteins. In some embodiments, the antibodies work synergistically to enhance efficacy by targeting more than one cell-surface protein.

In some embodiments, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope in a lineage-specific cell-surface antigen and one or more immunotherapeutic agents (e.g., antibodies) that target cells expressing the lineage-specific cell-surface antigen. In some embodiments, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope in a type 1 lineage-specific cell-surface antigen and one or more immunotherapeutic agents (e.g., antibodies) that target cells expressing the lineage-specific cell-surface antigen. In some embodiments, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope in a type 2 lineage-specific cell-surface antigen and one or more immunotherapeutic agents (e.g., antibodies) that target cells expressing the lineage-specific cell-surface antigen. In any of the embodiments described herein, one or more additional immunotherapeutic agents may be further administered to the subject (e.g., targeting one or more additional epitopes and/or antigens), for example if the hematopoietic malignancy relapses.

In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope of CD33 and one or more antibodies that target cells expressing CD33. In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells lacking an epitope in exon 2 or exon 3 of CD33 and one or more antibodies that target cells expressing CD33. In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells expressing a mutated CD33 comprising the amino acid sequence of SEQ ID NO: 56 or SEQ ID NO: 58 and one or more antibodies that target cells expressing CD33.

In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope of CD19 and one or more antibodies that target cells expressing CD19. In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells lacking an epitope in exon 2 or exon 4 of CD19 and one or more antibodies that target cells expressing CD19. In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells expressing a mutated CD19 comprising the amino acid sequence of SEQ ID NO: 52 or SEQ ID NO: 73 and one or more antibodies that target cells expressing CD19.

(ii) Immune Cells Expressing Chimeric Antigen Receptors

In some embodiments, the cytotoxic agent that targets an epitope of a lineage-specific cell-surface antigen as described herein is an immune cell that expresses a chimeric receptor, which comprises an antigen-binding fragment (e.g., a single-chain antibody) capable of binding to the epitope of the lineage-specific protein (e.g., CD33 or CD19). Recognition of a target cell (e.g., a cancer cell) having the epitope of the lineage-specific protein on its cell surface by the antigen-binding fragment of the chimeric receptor transduces an activation signal to the signaling domain(s) (e.g., co-stimulatory signaling domain and/or the cytoplasmic signaling domain) of the chimeric receptor, which may activate an effector function in the immune cell expressing the chimeric receptor. In some embodiments, the immune cell expresses more than one chimeric receptor (e.g., 2, 3, 4, 5 or more), referred to as a bispecific or multi-specific immune cell. In some embodiments, the immune cell expresses more than one chimeric receptor, at least one of which targets an epitope of a lineage-specific cell-surface antigen. In some embodiments, the immune cell expresses more than one chimeric receptor, each of which targets an epitope of a lineage-specific cell-surface antigen. In some embodiments, the immune cell expresses more than one chimeric receptor, at least one of which targets an epitope of a lineage-specific cell-surface antigen and at least one of which targets an epitope of an additional cell-surface antigen. In some embodiments, targeting of more than one lineage-specific cell-surface protein or a lineage-specific cell-surface protein and one or more additional cell-surface protein may reduce relapse of a hematopoietic malignancy. In some embodiments, the immune cell expresses a chimeric receptor that targets more than one epitopes (e.g., more than one epitopes of one antigen or epitopes of more than one antigen), referred to as a bispecific chimeric receptor.

In some embodiments, epitopes of two or more lineage-specific cell-surface proteins are targeted by cytotoxic agents. In some embodiments, two or more chimeric receptors are expressed in the same immune cell, e.g., bispecific chimeric receptors. Such cells can be used in any of the methods described herein. In some embodiments, cells expressing a chimeric receptor are “pooled”, i.e., two or more groups of cells express two or more different chimeric receptors. In some embodiments, two or more cells expressing different chimeric antigen receptors are administered concurrently. In some embodiments, two or more cells expressing different chimeric antigen receptors are administered sequentially. In some embodiments, epitopes of CD33 and CD19 are targeted by cytotoxic agents. In some embodiments, the chimeric receptors targeting CD33 and CD19 are expressed in the same immune cell (i.e., a bispecific immune cell). Such cells can be used in any of the methods described herein. In some embodiments, cells expressing chimeric receptors targeting CD33 and CD19 “pooled”, i.e., two or more groups of cells express two or more different chimeric receptors. In some embodiments, two or more groups of cells expressing chimeric receptors targeting CD33 and CD19 are administered concurrently. In some embodiments, two or more groups of cells expressing chimeric receptors targeting CD33 and CD19 are administered sequentially.

As used herein, a chimeric receptor refers to a non-naturally occurring molecule that can be expressed on the surface of a host cell and comprises binding domain that provides specificity of the chimeric receptor (e.g., an antigen-binding fragment that binds to an epitope of a cell-surface lineage-specific protein). In general, chimeric receptors comprise at least two domains that are derived from different molecules. In addition to the epitope-binding fragment described herein, the chimeric receptor may further comprise one or more of the following: a hinge domain, a transmembrane domain, a co-stimulatory domain, a cytoplasmic signaling domain, and combinations thereof. In some embodiments, the chimeric receptor comprises from N terminus to C terminus, an antigen-binding fragment that binds to a cell-surface lineage-specific protein, a hinge domain, a transmembrane domain, and a cytoplasmic signaling domain. In some embodiments, the chimeric receptor further comprises at least one co-stimulatory domain. See, e.g., Marin-Acevedo et al. J. Hematol. Oncol. (2018) 11: 8.

Alternatively or in addition, the chimeric receptor may be a switchable chimeric receptor. See. e.g., Rodger et al. PNAS (2016) 113: 459-468; Cao et al. Angew. Chem. Int. Ed. (2016) 55: 7520-7524. In general, a switchable chimeric receptor comprises a binding domain that binds a soluble antigen-binding fragment, which has antigen binding specificity and may be administered concomitantly with the immune cells.

In some embodiments, the chimeric receptor may be a masked chimeric receptor, which is maintained in an “off” state until the immune cell expressing the chimeric receptor is localized to a desired location in the subject. For example, the binding domain of the chimeric receptor (e.g., antigen-binding fragment) may be blocked by an inhibitory peptide that is cleaved by a protease present at a desired location in the subject.

In some embodiments, it may be advantageous to modulate the binding affinity of the binding domain (e.g., antigen-binding fragment). For example, in some instances, relapse of hematopoietic malignancies results due to the reduced expression of the targeted antigen on the surface of target cells (e.g., antigen escape) and the lower levels of antigen any be inefficient or less efficient in stimulating cytotoxicity of the target cells. See, e.g., Majzner et al. Cancer Discovery (2018) 8(10). In some embodiments, the binding affinity of the binding domain (e.g., antigen-binding fragment) may be enhanced, for example by mutating one or more amino acid residues of the binding domain. Binding domains having enhanced binding affinity to an antigen may result in immune cells that response to lower levels of antigen (lower antigen density) and reduce or prevent relapse.

In some embodiments, the chimeric receptors described herein comprise one or more hinge domain(s). In some embodiments, the hinge domain may be located between the antigen-binding fragment and a transmembrane domain. A hinge domain is an amino acid segment that is generally found between two domains of a protein and may allow for flexibility of the protein and movement of one or both of the domains relative to one another. Any amino acid sequence that provides such flexibility and movement of the antigen-binding fragment relative to another domain of the chimeric receptor can be used.

The hinge domain may contain about 10-200 amino acids, e.g., 15-150 amino acids, 20-100 amino acids, or 30-60 amino acids. In some embodiments, the hinge domain may be of about 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or 200 amino acids in length.

In some embodiments, the hinge domain is a hinge domain of a naturally occurring protein. Hinge domains of any protein known in the art to comprise a hinge domain are compatible for use in the chimeric receptors described herein. In some embodiments, the hinge domain is at least a portion of a hinge domain of a naturally occurring protein and confers flexibility to the chimeric receptor. In some embodiments, the hinge domain is of CD8α or CD28. In some embodiments, the hinge domain is a portion of the hinge domain of CD8α, e.g., a fragment containing at least 15 (e.g., 20, 25, 30, 35, or 40) consecutive amino acids of the hinge domain of CD8α or CD28.

Hinge domains of antibodies, such as an IgG, IgA, IgM, IgE, or IgD antibody, are also compatible for use in the chimeric receptors described herein. In some embodiments, the hinge domain is the hinge domain that joins the constant domains CH1 and CH2 of an antibody. In some embodiments, the hinge domain is of an antibody and comprises the hinge domain of the antibody and one or more constant regions of the antibody. In some embodiments, the hinge domain comprises the hinge domain of an antibody and the CH3 constant region of the antibody. In some embodiments, the hinge domain comprises the hinge domain of an antibody and the CH2 and CH3 constant regions of the antibody. In some embodiments, the antibody is an IgG, IgA, IgM, IgE, or IgD antibody. In some embodiments, the antibody is an IgG antibody. In some embodiments, the antibody is an IgG1, IgG2, IgG3, or IgG4 antibody. In some embodiments, the hinge region comprises the hinge region and the CH2 and CH3 constant regions of an IgG1 antibody. In some embodiments, the hinge region comprises the hinge region and the CH3 constant region of an IgG1 antibody.

Also within the scope of the present disclosure are chimeric receptors comprising a hinge domain that is a non-naturally occurring peptide. In some embodiments, the hinge domain between the C-terminus of the extracellular ligand-binding domain of an Fc receptor and the N-terminus of the transmembrane domain is a peptide linker, such as a (Gly_(x)Ser)n linker, wherein x and n, independently can be an integer between 3 and 12, including 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or more.

Additional peptide linkers that may be used in a hinge domain of the chimeric receptors described herein are known in the art. See, e.g., Wriggers et al. Current Trends in Peptide Science (2005) 80(6): 736-746 and PCT Publication WO 2012/088461.

In some embodiments, the chimeric receptors described herein may comprise one or more transmembrane domain(s). The transmembrane domain for use in the chimeric receptors can be in any form known in the art. As used herein, a “transmembrane domain” refers to any protein structure that is thermodynamically stable in a cell membrane, preferably a eukaryotic cell membrane. Transmembrane domains compatible for use in the chimeric receptors used herein may be obtained from a naturally occurring protein. Alternatively, the transmembrane domain may be a synthetic, non-naturally occurring protein segment, e.g., a hydrophobic protein segment that is thermodynamically stable in a cell membrane.

Transmembrane domains are classified based on the transmembrane domain topology, including the number of passes that the transmembrane domain makes across the membrane and the orientation of the protein. For example, single-pass membrane proteins cross the cell membrane once, and multi-pass membrane proteins cross the cell membrane at least twice (e.g., 2, 3, 4, 5, 6, 7 or more times). In some embodiments, the transmembrane domain is a single-pass transmembrane domain. In some embodiments, the transmembrane domain is a single-pass transmembrane domain that orients the N terminus of the chimeric receptor to the extracellular side of the cell and the C terminus of the chimeric receptor to the intracellular side of the cell. In some embodiments, the transmembrane domain is obtained from a single pass transmembrane protein. In some embodiments, the transmembrane domain is of CD8α. In some embodiments, the transmembrane domain is of CD28. In some embodiments, the transmembrane domain is of ICOS.

In some embodiments, the chimeric receptors described herein comprise one or more costimulatory signaling domains. The term “co-stimulatory signaling domain,” as used herein, refers to at least a portion of a protein that mediates signal transduction within a cell to induce an immune response, such as an effector function. The co-stimulatory signaling domain of the chimeric receptor described herein can be a cytoplasmic signaling domain from a co-stimulatory protein, which transduces a signal and modulates responses mediated by immune cells, such as T cells, NK cells, macrophages, neutrophils, or eosinophils.

In some embodiments, the chimeric receptor comprises more than one (at least 2, 3, 4, or more) co-stimulatory signaling domains. In some embodiments, the chimeric receptor comprises more than one co-stimulatory signaling domains obtained from different costimulatory proteins. In some embodiments, the chimeric receptor does not comprise a co-stimulatory signaling domain.

In general, many immune cells require co-stimulation, in addition to stimulation of an antigen-specific signal, to promote cell proliferation, differentiation and survival, and to activate effector functions of the cell. Activation of a co-stimulatory signaling domain in a host cell (e.g., an immune cell) may induce the cell to increase or decrease the production and secretion of cytokines, phagocytic properties, proliferation, differentiation, survival, and/or cytotoxicity. The co-stimulatory signaling domain of any co-stimulatory protein may be compatible for use in the chimeric receptors described herein. The type(s) of co-stimulatory signaling domain is selected based on factors such as the type of the immune cells in which the chimeric receptors would be expressed (e.g., primary T cells, T cell lines, NK cell lines) and the desired immune effector function (e.g., cytotoxicity). Examples of co-stimulatory signaling domains for use in the chimeric receptors can be the cytoplasmic signaling domain of co-stimulatory proteins, including, without limitation, CD27, CD28, 4-1BB, OX40, CD30, ICOS, CD2, CD7, LIGHT, NKG2C, B7-H3. In some embodiments, the co-stimulatory domain is derived from 4-1BB, CD28, or ICOS. In some embodiments, the costimulatory domain is derived from CD28 and chimeric receptor comprises a second co-stimulatory domain from 4-1BB or ICOS.

In some embodiments, the costimulatory domain is a fusion domain comprising more than one costimulatory domain or portions of more than one costimulatory domains. In some embodiments, the costimulatory domain is a fusion of costimulatory domains from CD28 and ICOS.

In some embodiments, the chimeric receptors described herein comprise one or more cytoplasmic signaling domain(s). Any cytoplasmic signaling domain can be used in the chimeric receptors described herein. In general, a cytoplasmic signaling domain relays a signal, such as interaction of an extracellular ligand-binding domain with its ligand, to stimulate a cellular response, such as inducing an effector function of the cell (e.g., cytotoxicity).

As will be evident to one of ordinary skill in the art, a factor involved in T cell activation is the phosphorylation of immunoreceptor tyrosine-based activation motif (ITAM) of a cytoplasmic signaling domain. Any ITAM-containing domain known in the art may be used to construct the chimeric receptors described herein. In general, an ITAM motif may comprise two repeats of the amino acid sequence YxxL/I separated by 6-8 amino acids, wherein each x is independently any amino acid, producing the conserved motif YxxL/Ix(6−8)YxxL/I. In some embodiments, the cytoplasmic signaling domain is from CD3ζ.

In some embodiments, the chimeric receptor described herein targets a type 2 protein. In some embodiments, the chimeric receptor targets CD33. In some embodiments, the chimeric receptor described herein targets a type 1 protein. In some embodiments, the chimeric receptor targets CD19. In some embodiments, the chimeric receptor targets a type 0 protein. Such a chimeric receptor may comprise an antigen-binding fragment (e.g., an scFv) comprising a heavy chain variable region and a light chain variable region that bind to CD19. Alternatively, the chimeric receptor may comprise an antigen-binding fragment (e.g., scFv) comprising a heavy chain variable region and a light chain variable region that bind to CD33.

In some embodiments, the immune cells described herein express a chimeric receptor (e.g., bispecific chimeric receptor) that targets a type 2 protein and a chimeric receptor that targets a type 1 protein. In some embodiments, the immune cells described herein express a chimeric receptor (e.g., bispecific chimeric receptor) that targets a type 2 protein and at least one additional cell-surface protein, such as any of those described herein. In some embodiments, the immune cells described herein express a chimeric receptor that targets CD33 and at least one additional cell-surface protein, such as any of those described herein. In some embodiments, the immune cells described herein express a chimeric receptor that targets a type 1 protein and at least one additional cell-surface protein, such as any of those described herein. In some embodiments, the immune cells described herein express a chimeric receptor that targets CD19 and at least one additional cell-surface protein, such as any of those described herein. In some embodiments, the chimeric receptor described herein targets CD33 and CD19.

In some embodiments, the immune cells described herein express a chimeric receptor that targets a type 2 protein and at least one additional chimeric receptor that targets an additional cell-surface protein, such as any of those described herein. In some embodiments, the immune cells described herein express a chimeric receptor that targets CD33 and at least one additional chimeric receptor that targets another cell-surface protein, such as any of those described herein. In some embodiments, the immune cells described herein express a chimeric receptor that targets a type 1 protein and at least one additional chimeric receptor that targets another cell-surface protein, such as any of those described herein. In some embodiments, the immune cells described herein express a chimeric receptor that targets CD19 and at least one additional chimeric receptor that targets another cell-surface protein, such as any of those described herein. In some embodiments, the immune cells express a chimeric receptor that targets CD33 and a chimeric receptor that targets CD19.

A chimeric receptor construct targeting CD33 and/or CD19 may further comprise at least a hinge domain (e.g., from CD28, CD8α, or an antibody), a transmembrane domain (e.g., from CD8α, CD28 or ICOS), one or more co-stimulatory domains (from one or more of CD28, ICOS, or 4-1BB) and a cytoplasmic signaling domain (e.g., from CD3ζ), or a combination thereof. In some examples, the methods described herein involve administering to a subject a population of genetically engineered hematopoietic cells and an immune cell expressing a chimeric receptor that targets CD33 and/or CD19, which may further comprise at least a hinge domain (e.g., from CD28, CD8α, or an antibody), a transmembrane domain (e.g., from CD8α, CD28 or ICOS), one or more co-stimulatory domains (from one or more of CD28, ICOS, or 4-1BB) and a cytoplasmic signaling domain (e.g., from CD3ζ, or a combination thereof.

Any of the chimeric receptors described herein can be prepared by routine methods, such as recombinant technology. Methods for preparing the chimeric receptors herein involve generation of a nucleic acid that encodes a polypeptide comprising each of the domains of the chimeric receptors, including the antigen-binding fragment and optionally, the hinge domain, the transmembrane domain, at least one co-stimulatory signaling domain, and the cytoplasmic signaling domain. In some embodiments, nucleic acids encoding the components of a chimeric receptor are joined together using recombinant technology.

Sequences of each of the components of the chimeric receptors may be obtained via routine technology, e.g., PCR amplification from any one of a variety of sources known in the art. In some embodiments, sequences of one or more of the components of the chimeric receptors are obtained from a human cell. Alternatively, the sequences of one or more components of the chimeric receptors can be synthesized. Sequences of each of the components (e.g., domains) can be joined directly or indirectly (e.g., using a nucleic acid sequence encoding a peptide linker) to form a nucleic acid sequence encoding the chimeric receptor, using methods such as PCR amplification or ligation. Alternatively, the nucleic acid encoding the chimeric receptor may be synthesized. In some embodiments, the nucleic acid is DNA. In other embodiments, the nucleic acid is RNA.

Mutation of one or more residues within one or more of the components of the chimeric receptor (e.g., the antigen-binding fragment, etc) may be performed prior to or after joining the sequences of each of the components. In some embodiments, one or more mutations in a component of the chimeric receptor may be made to modulate (increase or decrease) the affinity of the component for an epitope (e.g., the antigen-binding fragment for the target protein) and/or modulate the activity of the component.

Any of the chimeric receptors described herein can be introduced into a suitable immune cell for expression via conventional technology. In some embodiments, the immune cells are T cells, such as primary T cells or T cell lines. Alternatively, the immune cells can be NK cells, such as established NK cell lines (e.g., NK-92 cells). In some embodiments, the immune cells are T cells that express CD8 (CD8⁺) or CD8 and CD4 (CD8⁺/CD4⁺). In some embodiments, the T cells are T cells of an established T cell line, for example, 293T cells or Jurkat cells.

Primary T cells may be obtained from any source, such as peripheral blood mononuclear cells (PBMCs), bone marrow, tissues such as spleen, lymph node, thymus, or tumor tissue. A source suitable for obtaining the type of immune cells desired would be evident to one of skill in the art. In some embodiments, the population of immune cells is derived from a human patient having a hematopoietic malignancy, such as from the bone marrow or from PBMCs obtained from the patient. In some embodiments, the population of immune cells is derived from a healthy donor. In some embodiments, the immune cells are obtained from the subject to whom the immune cells expressing the chimeric receptors will be subsequently administered. Immune cells that are administered to the same subject from which the cells were obtained are referred to as autologous cells, whereas immune cells that are obtained from a subject who is not the subject to whom the cells will be administered are referred to as allogeneic cells.

The type of host cells desired may be expanded within the population of cells obtained by co-incubating the cells with stimulatory molecules, for example, anti-CD3 and anti-CD28 antibodies may be used for expansion of T cells.

To construct the immune cells that express any of the chimeric receptor constructs described herein, expression vectors for stable or transient expression of the chimeric receptor construct may be constructed via conventional methods as described herein and introduced into immune host cells. For example, nucleic acids encoding the chimeric receptors may be cloned into a suitable expression vector, such as a viral vector in operable linkage to a suitable promoter. The nucleic acids and the vector may be contacted, under suitable conditions, with a restriction enzyme to create complementary ends on each molecule that can pair with each other and be joined with a ligase. Alternatively, synthetic nucleic acid linkers can be ligated to the termini of the nucleic acid encoding the chimeric receptors. The synthetic linkers may contain nucleic acid sequences that correspond to a particular restriction site in the vector. The selection of expression vectors/plasmidsviral vectors would depend on the type of host cells for expression of the chimeric receptors, but should be suitable for integration and replication in eukaryotic cells.

In some embodiments, the chimeric receptors are expressed using a non-integrating transient expression system. In some embodiments, the chimeric receptors are integrated into the genome of the immune cell. In some embodiments, the chimeric receptors are integrated into a specific loci of the genome of immune cell using gene editing (e.g., zinc-finger nucleases, meganucleases, TALENs, CRISPR systems).

A variety of promoters can be used for expression of the chimeric receptors described herein, including, without limitation, cytomegalovirus (CMV) intermediate early promoter, a viral LTR such as the Rous sarcoma virus LTR, HIV-LTR, HTLV-1 LTR. Maloney murine leukemia virus (MMLV) LTR, myeloproliferative sarcoma virus (MPSV) LTR, spleen focus-forming virus (SFFV) LTR, the simian virus 40 (SV40) early promoter, herpes simplex tk virus promoter, elongation factor 1-alpha (EF1-α) promoter with or without the EF1-α intron. Additional promoters for expression of the chimeric receptors include any constitutively active promoter in an immune cell. Alternatively, any regulatable promoter may be used, such that its expression can be modulated within an immune cell. In some embodiments, the promoter regulating expression of a chimeric receptor is an inducible promoter. In general, the activity of “inducible promoters” may be regulated based on the presence (or absence) of a signal, such as an endogenous signal or an exogenous signal, for example a small molecule or drug that is administered to the subject.

Additionally, the vector may contain, for example, some or all of the following: a selectable marker gene, such as the neomycin gene for selection of stable or transient transfectants in host cells; enhancer/promoter sequences from the immediate early gene of human CMV for high levels of transcription: transcription termination and RNA processing signals from SV40 for mRNA stability; 5′- and 3′-untranslated regions for mRNA stability and translation efficiency from highly-expressed genes like α-globin or β-globin; SV40 polyoma origins of replication and ColE1 for proper episomal replication: internal ribosome binding sites (IRESes), versatile multiple cloning sites; T7 and SP6 RNA promoters for in vitro transcription of sense and antisense RNA; a “suicide switch” or “suicide gene” which when triggered causes cells carrying the vector to die (e.g., HSV thymidine kinase, an inducible caspase such as iCasp9, drug-induced suicide switch, monoclonal antibody mediated suicide switch), and reporter gene for assessing expression of the chimeric receptor. Suitable vectors and methods for producing vectors containing transgenes are well known and available in the art. Examples of the preparation of vectors for expression of chimeric receptors can be found, for example, in US2014/0106449, herein incorporated by reference in its entirety.

As will be appreciated by one of ordinary skill in the art, in some embodiments, it may be advantageous to quickly and efficiently reduce or eliminate the immune cells expressing chimeric receptors, for example at a time point following administration to a subject. Mechanisms of killing immune cells expressing chimeric receptors, or inducing cytotoxicity of such cells, are known in the art, see, e.g., Labanieh et al. Nature Biomedical Engineering (2018)2: 337-391; Slaney et al. Cancer Discovery (2018) 8(8): 924-934. In some embodiments, the immune cell expressing the chimeric receptor may also express a suicide switch” or “suicide gene,” which may or may not be encoded by the same vector as the chimeric receptor, as described above. In some embodiments, the immune cell expressing chimeric receptors further express an epitope tag such that upon engagement of the epitope tag, the immune cell is killed through antibody-dependent cell-mediated cytotoxicity and/or complement-mediated cytotoxicity. See, e.g., Paszkiewicz et al. J. Clin. Invest. (2016) 126: 4262-4272: Wang et al. Blood (2011) 118: 1255-1263; Tasian et al. Blood (2017) 129: 2395-2407; Philip et al. Blood (2014) 124: 1277-1287.

In some embodiments, the chimeric receptor construct or the nucleic acid encoding said chimeric receptor is a DNA molecule. In some embodiments, chimeric receptor construct or the nucleic acid encoding said chimeric receptor is a DNA vector and may be electroporated to immune cells (see, e.g., Till, et al. Blood (2012) 119(17): 3940-3950). In some embodiments, the nucleic acid encoding the chimeric receptor is an RNA molecule, which may be electroporated to immune cells.

Any of the vectors comprising a nucleic acid sequence that encodes a chimeric receptor construct described herein is also within the scope of the present disclosure. Such a vector may be delivered into host cells such as host immune cells by a suitable method. Methods of delivering vectors to immune cells are well known in the art and may include DNA, RNA, or transposon electroporation, transfection reagents such as liposomes or nanoparticles to delivery DNA, RNA, or transposons: delivery of DNA, RNA, or transposons or protein by mechanical deformation (see, e.g., Sharei et al. Proc. Natl. Acad Sci. USA (2013) 110(6): 2082-2087): or viral transduction. In some embodiments, the vectors for expression of the chimeric receptors are delivered to host cells by viral transduction. Exemplary viral methods for delivery include, but are not limited to, recombinant retroviruses (see, e.g., PCT Publication Nos. WO 90/07936; WO 94/03622; WO 93/25698; WO 93/25234; WO 93/11230; WO 93/10218; WO 91/02805: U.S. Pat. Nos. 5,219,740 and 4,777,127; GB Patent No. 2,200,651; and EP Patent No. 0 345 242), alphavirus-based vectors, and adeno-associated virus (AAV) vectors (see, e.g., PCT Publication Nos. WO 94/12649, WO 93/03769: WO 93/19191; WO 94/28938; WO 95/11984 and WO 95/00655). In some embodiments, the vectors for expression of the chimeric receptors are retroviruses. In some embodiments, the vectors for expression of the chimeric receptors are lentiviruses. In some embodiments, the vectors for expression of the chimeric receptors are adeno-associated viruses.

In examples in which the vectors encoding chimeric receptors are introduced to the host cells using a viral vector, viral particles that are capable of infecting the immune cells and carry the vector may be produced by any method known in the art and can be found, for example in PCT Application No. WO 1991/002805A2, WO 1998/009271 A1, and U.S. Pat. No. 6,194,191. The viral particles are harvested from the cell culture supernatant and may be isolated and/or purified prior to contacting the viral particles with the immune cells.

In some embodiments, the methods described herein involve use of immune cells that express more than one chimeric receptor (e.g., a chimeric receptors that target first epitope and chimeric receptors that target a second epitope). In some embodiments, more than one chimeric receptor (e.g., a chimeric receptors that target first epitope and chimeric receptors that target a second epitope) are expressed from a single vector. In some embodiments, more than one chimeric receptor (e.g., a chimeric receptors that target first epitope and chimeric receptors that target a second epitope) are expressed from a more than one vector. Such immune cells may be prepared using methods known in the art, for example by delivering a vector that encodes a first chimeric receptor simultaneously or sequentially with a second vector that encodes a second chimeric receptor. In some embodiments, the resulting immune cell population is a mixed population comprising a subset of immune cells that express one chimeric receptor and a subset of immune cells that express both chimeric receptors.

In some embodiments, the domains of the chimeric receptor are encoded by and expressed from a single vector. Alternatively, the domains of the chimeric receptor may be encoded by and expressed from more than one vector. In some embodiments, activity of immune cells expressing the chimeric receptors may be regulated by controlling assembly of the chimeric receptor. The domains of a chimeric receptor may be expressed as two or more non-functional segments of the chimeric receptor and induced to assemble at a desired time and/or location, for example through use of a dimerization agent (e.g., dimerizing drug).

The methods of preparing host cells expressing any of the chimeric receptors described herein may comprise activating and/or expanding the immune cells ex vivo. Activating a host cell means stimulating a host cell into an activate state in which the cell may be able to perform effector functions (e.g., cytotoxicity). Methods of activating a host cell will depend on the type of host cell used for expression of the chimeric receptors. Expanding host cells may involve any method that results in an increase in the number of cells expressing chimeric receptors, for example, allowing the host cells to proliferate or stimulating the host cells to proliferate. Methods for stimulating expansion of host cells will depend on the type of host cell used for expression of the chimeric receptors and will be evident to one of skill in the art. In some embodiments, the host cells expressing any of the chimeric receptors described herein are activated and/or expanded ex vivo prior to administration to a subject.

It has been appreciated that administration of immunostimulatory cytokines may enhance proliferation of immune cells expressing chimeric receptors following administration to a subject and/or promote engraftment of the immune cells. See, e.g., Pegram et al. Leukemia (2015) 29:415-422; Chinnasamy et al. Clin. Cancer Res. (2012) 18: 1672-1683; Krenciute et al. Cancer Immunol. Res. (2017) 5: 571-581; Hu et al. Cell Rep. (2017) 20: 3025-3033: Markley et al. Blood (2010) 115: 3508-3519). Any of the methods described herein may further involve administering one or more immunostimulatory cytokines concurrently with any of the immune cells expressing chimeric receptors. Non-limiting example of immunostimulatory cytokines include IL-12, IL-15, IL-1, IL-21, and combinations thereof.

Any anti-CD19 CAR and anti-CD33 CAR molecules known in the art can be used together with the genetically engineered HSCs described herein. Exemplary anti-CD19 CARs include axicabtagene and tisagenlecleucel. Exemplary anti-CD33 CARs include those disclosed in WO2017/066760 and WO2017/079400.

In one specific example, primary human CD8⁺ T cells are isolated from patients' peripheral blood by immunomagnetic separation (Miltenyi Biotec). T cells are cultured and stimulated with anti-CD3 and anti-CD28 mAbs-coated beads (Invitrogen) as previously described (Levine et al., J. Immunol. (1997) 159(12):5921).

Chimeric receptors that target a lineage-specific cell-surface proteins (e.g., CD19 or CD33) are generated using conventional recombinant DNA technologies and inserted into a lentiviral vector. The vectors containing the chimeric receptors are used to generate lentiviral particles, which are used to transduce primary CD8⁺ T cells. Human recombinant IL-2 may be added every other day (50 IU/mL). T cells are cultured for ˜14 days after stimulation. Expression of the chimeric receptors can be confirmed using methods, such as Western blotting and flow cytometry.

T cells expressing the chimeric receptors are selected and assessed for their ability to bind to the lineage-specific cell-surface protein such as CD19 or CD33 and to induce cytotoxicity of cells expressing the lineage-specific protein. Immune cells expressing the chimeric receptor are also evaluated for their ability to induce cytotoxicity of cells expressing the lineage-specific antigen in mutated form. Preferably, immune cells expressing chimeric receptors that binds to the wild-type lineage-specific protein but not the mutated form. (FIG. 3, using CD33 as an example).

The cells (e.g., hematopoietic stem cells) that express the mutated lineage-specific protein are also assessed for various characteristics, including proliferation, erythropoietic differentiation, and colony formation to confirm that the mutated lineage-specific protein retained the bioactivity as the wild-type counterpart.

The immune cells expressing one or more CAR-T receptors may be further modified genetically, for example, by knock-out of the native T-cell receptor (TCR) or an MHC chain and/or by introducing a new TCR. Alternatively, the immune cells may retain the native TCR loci.

In some embodiments, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope in a lineage-specific cell-surface antigen and one or more immunotherapeutic agents (e.g., immune cells expressing chimeric receptor(s)) that target cells expressing the lineage-specific cell-surface antigen. In some embodiments, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope in a type 1 lineage-specific cell-surface antigen and one or more immunotherapeutic agents (e.g., immune cells expressing chimeric receptor(s)) that target cells expressing the lineage-specific cell-surface antigen. In some embodiments, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope in a type 2 lineage-specific cell-surface antigen and one or more immunotherapeutic agents (e.g., immune cells expressing chimeric receptor(s)) that target cells expressing the lineage-specific cell-surface antigen. In any of the embodiments described herein, one or more additional immunotherapeutic agents may be further administered to the subject (e.g., targeting one or more additional epitopes and/or antigens), for example if the hematopoietic malignancy relapses.

In some embodiments, the methods described herein involve administering immune cells expressing chimeric receptors that target an epitope of a lineage-specific cell-surface protein that is mutated in the population of genetically engineered hematopoietic cells. In some embodiments, the methods described herein involve administering immune cells expressing chimeric receptors that target an epitope of a lineage-specific cell-surface protein that is mutated in the population of genetically engineered hematopoietic cells and one or more additional cytotoxic agents that may target one or more additional cell-surface proteins. In some embodiments, the agents could work synergistically to enhance efficacy by targeting more than one cell-surface protein.

In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope of CD33 and one or more immune cells expressing chimeric receptor(s) that target cells expressing CD33. In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells lacking an epitope in exon 2 or exon 3 of CD33 and one or more immune cells expressing chimeric receptor(s) that target cells expressing CD33. In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells expressing a mutated CD33 comprising the amino acid sequence of SEQ ID NO: 56 or SEQ ID NO: 58 and one or more immune cells expressing chimeric receptor(s) that target cells expressing CD33.

In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope of CD19 and one or more immune cells expressing chimeric receptor(s) that target cells expressing CD19. In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells lacking an epitope in exon 2 or exon 4 of CD19 and one or more immune cells expressing chimeric receptor(s) that target cells expressing CD19. In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells expressing a mutated CD19 comprising the amino acid sequence of SEQ ID NO: 52 or SEQ ID NO: 73 and one or more immune cells expressing chimeric receptor(s) that target cells expressing CD19.

(iii) Antibody-Drug Conjugate

In some embodiments, the cytotoxic agent targeting an epitope of a cell-surface lineage-specific protein is an antibody-drug conjugate (ADC). As will be evident to one of ordinary skill in the art, the term “antibody-drug conjugate” can be used interchangeably with “immunotoxin” and refers to a fusion molecule comprising an antibody (or antigen-binding fragment thereof) conjugated to a toxin or drug molecule. Binding of the antibody to the corresponding epitope of the target protein allows for delivery of the toxin or drug molecule to a cell that presents the protein (and epitope thereof) on the cell surface (e.g., target cell), thereby resulting in death of the target cell. In some embodiments, the antibody-drug conjugate (or antigen-binding fragment thereof) binds to its corresponding epitope of a lineage-specific cell-surface antigen but does not bind to a lineage-specific cell-surface antigen that lacks the epitope or in which the epitope has been mutated.

In some embodiments, the agent is an antibody-drug conjugate. In some embodiments, the antibody-drug conjugate comprises an antigen-binding fragment and a toxin or drug that induces cytotoxicity in a target cell. In some embodiments, the antibody-drug conjugate targets a type 2 protein. In some embodiments, the antibody-drug conjugate targets CD33. In some embodiments, the antibody-drug conjugate binds to an epitope in exon 2 or exon 3 of CD33. In some embodiments, the antibody-drug conjugate targets a type 1 protein. In some embodiments, the antibody-drug conjugate binds to an epitope in exon 2 or exon 4 of CD19. In some embodiments, the antibody-drug conjugate targets CD19. In some embodiments, the antibody-drug conjugate targets a type 0 protein.

Toxins or drugs compatible for use in antibody-drug conjugates are well known in the art and will be evident to one of ordinary skill in the art. See, e.g., Peters et al. Biosci. Rep. (2015) 35(4): e00225, Beck et al. Nature Reviews Drug Discovery (2017) 16:315-337; Marin-Acevedo et al. J. Hematol. Oncol. (2018) 11: 8; Elgundi et al. Advanced Drug Delivery Reviews (2017) 122: 2-19. In some embodiments, the antibody-drug conjugate may further comprise a linker (e.g., a peptide linker, such as a cleavable linker or a non-cleavable linker) attaching the antibody and drug molecule. Examples of antibody-drug conjugates include, without limitation, brentuximab vedotin, glembatumumab vedotin/CDX-011, depatuxizumab mafodotin/ABT-414, PSMA ADC, polatuzumab vedotin/RG7596/DCDS4501A, denintuzumab mafodotin/SGN-CD19A, AGS-16C3F, CDX-014, RG7841/DLYE5953A, RG7882/DMUC406A, RG7986/DCDS0780A, SGN-LIV1A, enfortumab vedotin/ASG-22ME, AG-15ME, AGS67E, telisotuzumab vedotin/ABBV-399, ABBV-221, ABBV-085, GSK-2857916, tisotumab vedotin/HuMax-TF-ADC, HuMax-Axl-ADC, pinatuzumab veodtin/RG7593/DCDT2980S, lifastuzumab vedotin/RG7599/DNIB0600A, indusatumab vedotin/MLN-0264/TAK-264, vandortuzumab vedotin/RG7450/DSTP3086S, sofituzumab vedotin/RG7458/DMUC5754A, RG7600/DMOT4039A, RG7336/DEDN6526A, ME1547, PF-06263507/ADC 5T4, trastuzumab emtansine/T-DM1, mirvetuximab soravtansine/IMGN853, coltuximab ravtansine/SAR3419, naratuximab emtansine/IMGN529, indatuximab ravtansine/BT-062, anetumab ravtansine/BAY94-9343, SAR408701, SAR428926, AMG 224, PCA062, HKT288, LY3076226, SAR566658, lorvotuzumab mertansine/IMGN901, cantuzumab mertansine/SB-408075, cantuzumab ravtansine/IMGN242, laprituximab emtansine/IMGN289, IMGN388, bivatuzumab mertansine, AVE9633, BIIB015, MLN2704, AMG 172, AMG 595, LOP 628, vadastuximab talirine/SGN-CD33A, SGN-CD70A, SGN-CD19B, SGN-CD123A. SGN-CD352A, rovalpituzumab tesirine/SC 16LD6.5, SC-002, SC-003, ADCT-301/HuMax-TAC-PBD, ADCT-402, MEDI3726/ADC-401, IMGN779, IMGN632, gemtuzumab ozogamicin, inotuzumab ozogamicin/CMC-544, PF-06647263, CMD-193, CMB-401, trastuzumab duocarmazine/SYD985, BMS-936561/MDX-1203, sacituzumab govitecan/IMMU-132, labetuzumab govitecanlIMMU-130, DS-8201a, U3-1402, milatuzumab doxorubicin/IMMU-110/hLL1-DOX, BMS-986148, RC48-ADC/hertuzumab-vc-MMAE, PF-06647020, PF-06650808, PF-06664178/RN927C, lupartumab amadotin/BAY1129980, aprutumab ixadotin/BAY1187982, ARX788, AGS62P1, XMT-1522, AbGn-107, MEDI4276, DSTA4637S/RG7861. In one example, the antibody-drug conjugate is gemtuzumab ozogamicin.

In some embodiments, binding of the antibody-drug conjugate to the epitope of the cell-surface lineage-specific protein induces internalization of the antibody-drug conjugate, and the drug (or toxin) may be released intracellularly. In some embodiments, binding of the antibody-drug conjugate to the epitope of a cell-surface lineage-specific protein induces internalization of the toxin or drug, which allows the toxin or drug to kill the cells expressing the lineage-specific protein (target cells). In some embodiments, binding of the antibody-drug conjugate to the epitope of a cell-surface lineage-specific protein induces internalization of the toxin or drug, which may regulate the activity of the cell expressing the lineage-specific protein (target cells). The type of toxin or drug used in the antibody-drug conjugates described herein is not limited to any specific type.

In some embodiments, two or more (e.g., 2, 3, 4, 5 or more) epitopes of a lineage-specific cell-surface antigen have been modified, enabling two or more (e.g., 2, 3, 4, 5 or more) different cytotoxic agents (e.g., two ADCs) to be targeted to the two or more epitopes. In some embodiments, the toxins carried by the ADCs could work synergistically to enhance efficacy (e.g., death of the target cells). In some embodiments, epitopes of two or more (e.g., 2, 3, 4, 5 or more) lineage-specific cell surface protein have been modified, enabling two or more (e.g., 2, 3, 4, 5 or more) different cytotoxic agents (e.g., two ADCs) to be targeted to epitopes of the two or more lineage-specific cell-surface antigens. In some embodiments, one or more (e.g., 1, 2, 3, 4, 5 or more) epitopes of a lineage-specific cell-surface antigen have been modified and one or more (e.g., 1, 2, 3, 4, 5 or more) epitopes of an additional cell-surface protein have been modified, enabling two or more (e.g., 2, 3, 4, 5 or more) different cytotoxic agents (e.g., two ADCs) to be targeted to epitopes of the lineage-specific cell-surface antigen and epitopes of additional cell-surface antigen. In some embodiments, targeting of more than one lineage-specific cell-surface antigen or a lineage-specific cell-surface antigen and one or more additional cell-surface protein/antigen may reduce relapse of a hematopoietic malignancy.

In some embodiments, the methods described herein involve administering ADCs that target an epitope of a lineage-specific cell-surface antigen that is mutated in the population of genetically engineered hematopoietic cells. In some embodiments, the methods described herein involve administering ADCs that target an epitope of a lineage-specific cell-surface antigen that is mutated in the population of genetically engineered hematopoietic cells and one or more additional cytotoxic agents that may target one or more additional cell-surface proteins. In some embodiments, the agents could work synergistically to enhance efficacy by targeting more than one cell-surface protein.

An ADC described herein may be used as a follow-on treatment to subjects who have been undergone the combined therapy as described herein.

In some embodiments, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope in a lineage-specific cell-surface antigen and one or more immunotherapeutic agents (e.g., ADCs) that target cells expressing the lineage-specific cell-surface antigen. In some embodiments, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope in a type 1 lineage-specific cell-surface antigen and one or more immunotherapeutic agents (e.g., ADCs) that target cells expressing the lineage-specific cell-surface antigen. In some embodiments, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope in a type 2 lineage-specific cell-surface antigen and one or more immunotherapeutic agents (e.g., ADCs) that target cells expressing the lineage-specific cell-surface antigen. In any of the embodiments described herein, one or more additional immunotherapeutic agents may be further administered to the subject (e.g., targeting one or more additional epitopes and/or antigens), for example if the hematopoietic malignancy relapses.

In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope of CD33 and one or more antibody-drug conjugates that target cells expressing CD33. In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells lacking an epitope in exon 2 or exon 3 of CD33 and one or more antibodies antibody-drug conjugates that target cells expressing CD33. In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells expressing a mutated CD33 comprising the amino acid sequence of SEQ ID NO: 56 or SEQ ID NO: 58 and one or more antibody-drug conjugates that target cells expressing CD33.

In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells lacking a non-essential epitope of CD19 and one or more antibody-drug conjugates that target cells expressing CD19. In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells lacking an epitope in exon 2 or exon 4 of CD19 and one or more antibody-drug conjugates that target cells expressing CD19. In some examples, the methods described herein involve administering to the subject a population of genetically engineered cells expressing a mutated CD19 comprising the amino acid sequence of SEQ ID NO: 52 or SEQ ID NO: 73 and one or more antibody-drug conjugates that target cells expressing CD19.

III. Methods of Treatment and Combination Therapies

The genetically engineered hematopoietic cells such as HSCs may be administered to a subject in need of the treatment, either taken alone or in combination of one or more cytotoxic agents that target one or more lineage-specific cell-surface antigens as described herein. Since the hematopoietic cells are genetically edited in the genes of the one or more lineage-specific cell-surface antigens, the hematopoietic cells and/or descendant cells thereof would express the one or more lineage-specific cell-surface antigens in mutated form (e.g., but functional) such that they can escape being targeted by the cytotoxic agents, for example, CAR-T cells.

Thus, the present disclosure provides methods for treating a hematopoietic malignancy, the method comprising administering to a subject in need thereof (i) a population of the genetically engineered hematopoietic cells described herein, and optionally (ii) a cytotoxic agent such as CAR-T cells that target a lineage-specific cell-surface antigen, the gene of which is genetically edited in the hematopoietic cells such that the cytotoxic agent does not target hematopoietic cells or descendant cells thereof. The administration of(i) and (ii) may be concurrently or in any order. In some embodiments, the cytotoxic agents and/or the hematopoietic cells may be mixed with a pharmaceutically acceptable carrier to form a pharmaceutical composition, which is also within the scope of the present disclosure.

In some embodiments, the genetically engineered hematopoietic stem cells have genetic editing in genes of at least two lineage-specific cell-surface proteins/antigens A and B. Such hematopoietic stem cells can be administered to a subject, who has been or will be treated with a first cytotoxic agent specific to A (e.g., anti-protein A CAR-T cells), or who is at risk of a hematopoietic malignancy that would need treatment of the cytotoxic agent. When the subject developed resistance to the cytotoxic agent after the treatment or has relapse of the hematopoietic malignancy, a second cytotoxic agent specific to B (e.g., anti-protein B CAR-T cells) may be administered to the subject. Because the genetically engineered hematopoietic cells have genetic editing in both A and B genes, those cells and descendant cells thereof would also be resistant to cytotoxicity induced by the second cytotoxic agent. As such, administering once the genetically engineered hematopoietic cells would be sufficient to compensate loss of normal cells expressing at least lineage-specific cell-surface proteins/antigens A and B due to multiple treatment by cytotoxic agents specific to at least proteins/antigens A and B.

As used herein, “subject,” “individual,” and “patient” are used interchangeably, and refer to a vertebrate, preferably a mammal such as a human. Mammals include, but are not limited to, human primates, non-human primates or murine, bovine, equine, canine or feline species. In some embodiments, the subject is a human patient having a hematopoietic malignancy.

To perform the methods described herein, an effective amount of the genetically engineered hematopoietic cells can be administered to a subject in need of the treatment. Optionally, the hematopoietic cells can be co-used with a cytotoxic agent as described herein. As used herein the term “effective amount” may be used interchangeably with the term “therapeutically effective amount” and refers to that quantity of a cytotoxic agent, hematopoietic cell population, or pharmaceutical composition (e.g., a composition comprising cytotoxic agents and/or hematopoietic cells) that is sufficient to result in a desired activity upon administration to a subject in need thereof. Within the context of the present disclosure, the term “effective amount” refers to that quantity of a compound, cell population, or pharmaceutical composition that is sufficient to delay the manifestation, arrest the progression, relieve or alleviate at least one symptom of a disorder treated by the methods of the present disclosure. Note that when a combination of active ingredients is administered the effective amount of the combination may or may not include amounts of each ingredient that would have been effective if administered individually.

Effective amounts vary, as recognized by those skilled in the art, depending on the particular condition being treated, the severity of the condition, the individual patient parameters including age, physical condition, size, gender and weight, the duration of the treatment, the nature of concurrent therapy (if any), the specific route of administration and like factors within the knowledge and expertise of the health practitioner. In some embodiments, the effective amount alleviates, relieves, ameliorates, improves, reduces the symptoms, or delays the progression of any disease or disorder in the subject. In some embodiments, the subject is a human. In some embodiments, the subject is a human patient having a hematopoietic malignancy.

As described herein, the hematopoietic cells and/or immune cells expressing chimeric receptors may be autologous to the subject, i.e., the cells are obtained from the subject in need of the treatment, manipulated such that the cells do not bind the cytotoxic agents, and then administered to the same subject. Administration of autologous cells to a subject may result in reduced rejection of the host cells as compared to administration of non-autologous cells. Alternatively, the host cells are allogeneic cells, i.e., the cells are obtained from a first subject, manipulated such that the cells do not bind the cytotoxic agents, and then administered to a second subject that is different from the first subject but of the same species. For example, allogeneic immune cells may be derived from a human donor and administered to a human recipient who is different from the donor.

In some embodiments, engineered hematopoietic cells comprising one or more genetically engineered gene(s) encoding lineage-specific cell-surface protein(s) (e.g., CD33 or CD19 or another lineage-specific cell-surface protein described herein) and the immune cells engineered to target an epitope of the lineage-specific cell-surface protein(s) are both allogeneic to the subject. In some embodiments, engineered hematopoietic cells comprising one or more genetically engineered gene(s) encoding lineage-specific cell-surface protein(s) (e.g., CD33 or CD19 or another lineage-specific cell-surface protein described herein) and the immune cells engineered to target an epitope of the lineage-specific cell-surface protein(s) are from the same allogeneic donor. In some embodiments, engineered hematopoietic cells comprising one or more genetically engineered gene(s) encoding lineage-specific cell-surface protein(s) (e.g., CD33 or CD19 or another lineage-specific cell-surface protein described herein) and the immune cells engineered to target an epitope of the lineage-specific cell-surface protein(s) are from two different allogeneic donors.

In some embodiments, engineered hematopoietic cells comprising one or more genetically engineered gene(s) encoding lineage-specific cell-surface protein(s) (e.g., CD33 or CD19 or another lineage-specific cell-surface protein described herein) and the immune cells engineered to target an epitope of the lineage-specific cell-surface protein(s) are both autologous to the subject.

In some embodiments, engineered hematopoietic cells comprising one or more genetically engineered gene(s) encoding lineage-specific cell-surface protein(s) (e.g., CD33 or CD19 or another lineage-specific cell-surface protein described herein) are autologous to the subject and the immune cells engineered to target an epitope of the lineage-specific cell-surface protein(s) are from an allogeneic donor. In some embodiments, engineered hematopoietic cells comprising one or more genetically engineered gene(s) encoding lineage-specific cell-surface protein(s) (e.g., CD33 or CD19 or another lineage-specific cell-surface protein described herein) are from an allogeneic donor and the immune cells engineered to target an epitope of the lineage-specific cell-surface protein(s) are autologous to the subject.

In some embodiments, the immune cells and/or hematopoietic cells are allogeneic cells and have been further genetically engineered to reduce graft-versus-host disease. For example, as described herein, the hematopoietic stem cells may be genetically engineered (e.g., using genome editing) to have reduced expression of CD45RA. Methods for reducing graft-versus-host disease are known in the art, see, e.g., Yang et al. Curr. Opin. Hematol. (2015) 22(6): 509-515. In some embodiments, the immune cells (e.g., T cells) may be genetically engineered to reduce or eliminate expression of the T cell receptor (TCR) or reduce or eliminate cell surface localization of the TCR. In some examples, the gene encoding the TCR is knocked out or silenced (e.g., using gene editing methods, or shRNAs). In some embodiments, the TCR is silenced using peptide inhibitors of the TCR. In some embodiments, the immune cells (e.g., T cells) are subjected to a selection process to select for immune cells or a population of immune cells that do not contain an alloreactive TCR. Alternatively, in some embodiments, immune cells that naturally do not express TCRs (e.g., NK cells) may be used in any of the methods described herein.

In some embodiments, the immune cells and/or hematopoietic cells have been further genetically engineered to reduce host-versus-graft effects. For example, in some embodiments, immune cells and/or hematopoietic cells may be subjected to gene editing or silencing methods to reduce or eliminate expression of one or more proteins involved in inducing host immune responses, e.g., CD52, MHC molecules, and/or MHC beta-2 microglobulin.

In some embodiments, the immune cells expressing any of the chimeric receptors described herein are administered to a subject in an amount effective in to reduce the number of target cells (e.g., cancer cells) by least 20%, e.g., 50, 80%, 100%, 2-fold, 5-fold, 10-fold, 20-fold, 50-fold, 100-fold or more.

A typical amount of cells, i.e., immune cells or hematopoietic cells, administered to a mammal (e.g., a human) can be, for example, in the range of about 10⁶ to 10¹¹ cells. In some embodiments it may be desirable to administer fewer than 10⁶ cells to the subject. In some embodiments, it may be desirable to administer more than 10¹¹ cells to the subject. In some embodiments, one or more doses of cells includes about 10⁶ cells to about 10¹¹ cells, about 10⁷ cells to about 10¹⁰ cells, about 10⁸ cells to about 10⁹ cells, about 10⁶ cells to about 10⁸ cells, about 10⁷ cells to about 10⁹ cells, about 10⁷ cells to about 10¹⁰ cells, about 10⁷ cells to about 10¹¹ cells, about 10⁸ cells to about 10¹⁰ cells, about 10⁸ cells to about 10¹¹ cells, about 10⁹ cells to about 10¹⁰ cells, about 10⁹ cells to about 10¹¹ cells, or about 10¹⁰ cells to about 10¹⁰ cells.

In some embodiments, the subject is preconditioned prior to administration of the cytotoxic agent and/or hematopoietic cells. In some embodiments, the method further comprises pre-conditioning the subject. In general, preconditioning a subject involves subjecting the patient to one or more therapy, such as a chemotherapy or other type of therapy, such as irradiation. In some embodiments, the preconditioning may induce or enhance the patient's tolerance of one or more subsequent therapy (e.g., a targeted therapy), as described herein. In some embodiments, the pre-conditioning involves administering one or more chemotherapeutic agents to the subject. Non-limiting examples of chemotherapeutic agents include actinomycin, azacitidine, azathioprine, bleomycin, bortezomib, carboplatin, capecitabine, cisplatin, chlorambucil, cyclophosphamide, cytarabine, daunorubicin, docetaxel, doxifluridine, doxorubicin, epirubicin, epothilone, etoposide, fludarabine, fluorouracil, gemcitabine, hydroxyurea, idarubicin, imatinib, irinotecan, mechlorethamine, mercaptopurine, methotrexate, mitoxantrone, oxaliplatin, paclitaxel, pemetrexed, teniposide, tioguanine, topotecan, valrubicin, vinblastine, vincristine, vindesine, and vinorelbine.

In some embodiments, the subject is preconditioned at least one day, two days, three days, four days, 5 days, 6 days, 7 days, 8 days, 9 days, 10 days, 11 days, 12 days, 13 days, two weeks, three weeks, four weeks, five weeks, six weeks, seven weeks, eight weeks, nine weeks, ten weeks, two months, three months, four months, five months, or at least six months prior to administering the cytotoxic agent and/or hematopoietic cells.

In other embodiments, the chemotherapy(ies) or other therapy(ies) are administered concurrently with the cytotoxic agent and manipulated hematopoietic cells. In other embodiments, the chemotherapy(ies) or other therapy(ies) are administered after the cytotoxic agent and manipulated hematopoietic cells.

In one embodiment, the chimeric receptor (e.g., a nucleic acid encoding the chimeric receptor) is introduced into an immune cell, and the subject (e.g., human patient) receives an initial administration or dose of the immune cells expressing the chimeric receptor. One or more subsequent administrations of the cytotoxic agent (e.g., immune cells expressing the chimeric receptor) may be provided to the patient at intervals of 15 days, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, or 2 days after the previous administration. More than one dose of the cytotoxic agent can be administered to the subject per week, e.g., 2, 3, 4, or more administrations of the agent. The subject may receive more than one doses of the cytotoxic agent (e.g., an immune cell expressing a chimeric receptor) per week, followed by a week of no administration of the agent, and finally followed by one or more additional doses of the cytotoxic agent (e.g., more than one administration of immune cells expressing a chimeric receptor per week). The immune cells expressing a chimeric receptor may be administered every other day for 3 administrations per week for two, three, four, five, six, seven, eight or more weeks.

Any of the methods described herein may be for the treatment of a hematological malignancy in a subject. As used herein, the terms “treat,” “treating,” and “treatment” mean to relieve or alleviate at least one symptom associated with the disease or disorder, or to slow or reverse the progression of the disease or disorder. Within the meaning of the present disclosure, the term “treat” also denotes to arrest, delay the onset (i.e., the period prior to clinical manifestation of a disease) and/or reduce the risk of developing or worsening a disease. For example, in connection with cancer, the term “treat” may mean eliminate or reduce the number or replication of cancer cells, and/or prevent, delay or inhibit metastasis, etc.

In some embodiments, a population of genetically engineered hematopoietic cells (e.g., carrying genetic edits in genes of one or more lineage-specific cell-surface proteins for expressing those proteins in mutated form) and a cytotoxic agent(s) specific to the lineage-specific cell-surface protein are co-administered to a subject via a suitable route (e.g., infusion). In such a combined therapeutic methods, the cytotoxic agent recognizes (binds) a target cell expressing the cell-surface lineage-specific protein for targeted killing. The hematopoietic cells that express the protein in mutated form, which has reduced binding activity or do not bind the cytotoxic acid (e.g., because of lacking binding epitope) allow for repopulation of a cell type that is targeted by the cytotoxic agent.

In some embodiments, the methods described herein involve administering a population of genetically engineered hematopoietic cells to a subject and administering one or more immunotherapeutic agents (e.g., cytotoxic agents). As will be appreciated by one of ordinary skill in the art, the immunotherapeutic agents may be of the same or different type (e.g., therapeutic antibodies, populations of immune cells expressing chimeric antigen receptor(s), and/or antibody-drug conjugates).

In some embodiments, the methods described herein involve administering a population of genetically engineered hematopoietic cells in which CD33 is mutated to a subject and administering one or immunotherapeutic agents (e.g., cytotoxic agents). In some embodiments, the methods described herein involve administering a population of genetically engineered hematopoietic cells in which CD33 is mutated to a subject and administering one or more therapeutic antibodies. In some embodiments, the methods described herein involve administering a population of genetically engineered hematopoietic cells in which CD33 is mutated to a subject and administering one or more populations of immune cells expressing chimeric antigen receptor(s). In some embodiments, the methods described herein involve administering a population of genetically engineered hematopoietic cells in which CD33 is mutated to a subject and administering one or more antibody-drug conjugates. In some embodiments, the methods described herein involve administering a population of genetically engineered hematopoietic cells comprising a mutated CD33 set forth by SEQ ID NO: 56 or 58 to a subject and administering one or more antibody-drug conjugates.

In some embodiments, the methods described herein involve administering a population of genetically engineered hematopoietic cells in which CD19 is mutated to a subject and administering one or immunotherapeutic agents (e.g., cytotoxic agents). In some embodiments, the methods described herein involve administering a population of genetically engineered hematopoietic cells in which CD19 is mutated to a subject and administering one or more therapeutic antibodies. In some embodiments, the methods described herein involve administering a population of genetically engineered hematopoietic cells in which CD19 is mutated to a subject and administering one or more populations of immune cells expressing chimeric antigen receptor(s). In some embodiments, the methods described herein involve administering a population of genetically engineered hematopoietic cells in which CD19 is mutated to a subject and administering one or more antibody-drug conjugates. In some embodiments, the methods described herein involve administering a population of genetically engineered hematopoietic cells comprising a mutated CD19 set forth by SEQ ID NO: 52 or 73 to a subject and administering one or more antibody-drug conjugates.

In some embodiments, the treatment of the patient can involve the following steps: (1) administering a therapeutically effective amount of the cytotoxic agent to the patient and (2) infusing or reinfusing the patient with hematopoietic stem cells, either autologous or allogenic. In some embodiments, the treatment of the patient can involve the following steps: (1) administering a therapeutically effective amount of an immune cell expressing a chimeric receptor to the patient, wherein the immune cell comprises a nucleic acid sequence encoding a chimeric receptor that binds an epitope of a cell-surface lineage-specific, disease-associated protein, and (2) infusing or reinfusing the patient with hematopoietic cells (e.g., hematopoietic stem cells), either autologous or allogenic. In each of the methods described herein, the cytotoxic agent (e.g., CAR-T cells) and the genetically engineered hematopoietic cells can be administered to the subject in any order. In some instances, the hematopoietic cells are given to the subject prior to the cytotoxic agent. In some instances, a second cytotoxic agent can be administered to the subject after treatment with the first cytotoxic agent, e.g., when the patient develops resistance or disease relapse. The hematopoietic cells given the same subject may have multiple edited genes expressing lineage-specific cell-surface proteins in mutated form such that the cytotoxic agents can target wild-type proteins but not the mutated form.

The efficacy of the therapeutic methods using a population of genetically engineered hematopoietic cells described herein, optionally in combination with a cytotoxic agent (e.g., CART) may be assessed by any method known in the art and would be evident to a skilled medical professional. For example, the efficacy of the therapy may be assessed by survival of the subject or cancer burden in the subject or tissue or sample thereof. In some embodiments, the efficacy of the therapy is assessed by quantifying the number of cells belonging to a particular population or lineage of cells. In some embodiments, the efficacy of the therapy is assessed by quantifying the number of cells presenting the cell-surface lineage-specific protein.

In some embodiments, the cytotoxic agent comprising an antigen-binding fragment that binds to the epitope of the cell-surface lineage-specific protein and the population of hematopoietic cells is administered concomitantly.

In some embodiments, the cytotoxic agent comprising an antigen-binding fragment that binds an epitope of a cell-surface lineage-specific protein (e.g., immune cells expressing a chimeric receptor as described herein) is administered prior to administration of the hematopoietic cells. In some embodiments, the agent comprising an antigen-binding fragment that binds an epitope of a cell-surface lineage-specific protein (e.g., immune cells expressing a chimeric receptor as described herein) is administered at least about 1 day, 2 days, 3 days, 4 days, 5 days, 6 days, 1 week, 2 weeks, 3 weeks, 4 weeks, 5 weeks, 6 weeks, 7 weeks, 8 weeks, 9 weeks, 10 weeks, 11 weeks, 12 weeks, 3 months, 4 months, 5 months, 6 months or more prior to administration of the hematopoietic cells.

In some embodiments, the hematopoietic cells are administered prior to the cytotoxic agent comprising an antigen-binding fragment that binds an epitope of the cell-surface lineage-specific protein (e.g., immune cells expressing a chimeric receptor as described herein). In some embodiments, the population of hematopoietic cells is administered at least about 1 day, 2 days, 3 days, 4 days, 5 days, 6 days, 1 week, 2 weeks, 3 weeks, 4 weeks, 5 weeks, 6 weeks, 7 weeks, 8 weeks, 9 weeks, 10 weeks, 11 weeks, 12 weeks, 3 months, 4 months, 5 months, 6 months or more prior to administration of the cytotoxic agent comprising an antigen-binding fragment that binds to an epitope of the cell-surface lineage-specific protein.

In some embodiments, the cytotoxic agent targeting the cell-surface lineage-specific protein and the population of hematopoietic cells are administered at substantially the same time. In some embodiments, the cytotoxic agent targeting the cell-surface lineage-specific protein is administered and the patient is assessed for a period of time, after which the population of hematopoietic cells is administered. In some embodiments, the population of hematopoietic cells is administered and the patient is assessed for a period of time, after which the cytotoxic agent targeting the cell-surface lineage-specific protein is administered.

Also within the scope of the present disclosure are multiple administrations (e.g., doses) of the cytotoxic agents and/or populations of hematopoietic cells. In some embodiments, the cytotoxic agents and/or populations of hematopoietic cells are administered to the subject once. In some embodiments, cytotoxic agents and/or populations of hematopoietic cells are administered to the subject more than once (e.g., at least 2, 3, 4, 5, or more times). In some embodiments, the cytotoxic agents and/or populations of hematopoietic cells are administered to the subject at a regular interval, e.g., every six months.

In some embodiments, the subject is a human subject having a hematopoietic malignancy. As used herein a hematopoietic malignancy refers to a malignant abnormality involving hematopoietic cells (e.g., blood cells, including progenitor and stem cells). Examples of hematopoietic malignancies include, without limitation, Hodgkin's lymphoma, non-Hodgkin's lymphoma, leukemia, or multiple myeloma. Exemplary leukemias include, without limitation, acute myeloid leukemia, acute lymphoid leukemia, chronic myelogenous leukemia, acute lymphoblastic leukemia or chronic lymphoblastic leukemia, and chronic lymphoid leukemia.

In some embodiments, cells involved in the hematopoietic malignancy are resistant to convention or standard therapeutics used to treat the malignancy. For example, the cells (e.g., cancer cells) may be resistant to a chemotherapeutic agent and/or CAR T cells used to treat the malignancy.

In some embodiments, the hematopoietic malignancy is associated with CD19+ cells. Examples include, but are not limited to, B cell malignancies such as non-Hodgkin's lymphoma. Hodgkin's lymphoma, leukemia, multiple myeloma, acute lymphoblastic leukemia, acute lymphoid leukemia, acute lymphocytic leukemia, chronic lymphoblastic leukemia, chronic lymphoid leukemia, and chronic lymphocytic leukemia. In some embodiments, the hematopoietic malignancy is a relapsing hematopoietic malignancy.

In some embodiments, the leukemia is acute myeloid leukemia (AML). AML is characterized as a heterogeneous, clonal, neoplastic disease that originates from transformed cells that have progressively acquired critical genetic changes that disrupt key differentiation and growth-regulatory pathways. (Dohner et al., NEJM, (2015) 373:1136). CD33 glycoprotein is expressed on the majority of myeloid leukemia cells as well as on normal myeloid and monocytic precursors and has been considered to be an attractive target for AML therapy (Laszlo et al., Blood Rev. (2014) 28(4): 143-53). While clinical trials using anti-CD33 monoclonal antibody based therapy have shown improved survival in a subset of AML patients when combined with standard chemotherapy, these effects were also accompanied by safety and efficacy concerns.

In some cases, a subject may initially respond to a therapy (e.g., for a hematopoietic malignancy) and subsequently experience relapse. Any of the methods or populations of genetically engineered hematopoietic cells described herein may be used to reduce or prevent relapse of a hematopoietic malignancy. Alternatively or in addition, any of the methods described herein may involve administering any of the populations of genetically engineered hematopoietic cells described herein and an immunotherapeutic agent (e.g., cytotoxic agent) that targets cells associated with the hematopoietic malignancy and further administering one or more additional immunotherapeutic agents when the hematopoietic malignancy relapses.

As used herein, the term “relapse” refers to the reemergence or reappearance of cells associated with a hematopoietic malignancy following a period of responsiveness to a therapy. Methods of determining whether a hematopoietic malignancy has relapsed in a subject will appreciated by one of ordinary skill in the art. In some embodiments, the period of responsiveness to a therapy involves the level or quantity of cells associated with the hematopoietic malignancy the falling below a threshold, e.g., below 20%, 15%, 10%, 5%, 4%, 3%, 2%, or 1% of the level or quantity of cells prior to administration of the therapy. In some embodiments, a relapse is characterized by the level or quantity of cells associated with the hematopoietic malignancy above a threshold, e.g., above 20%, 15%, 10%, 5%, 4%, 3%, 2%, or 1% higher than the level or quantity of cells during the period of responsiveness. Methods of determining the minimal residual disease in a subject are known in the art and may be used, for example to assess whether a hematopoietic malignancy has relapsed or is likely to relapse. See, e.g., Taraseviciute et al. Hematology and Oncology (2019) 31(1)).

In some embodiments, the subject has or is susceptible to relapse of a hematopoietic malignancy (e.g., AML) following administration of one or more previous therapies. In some embodiments, the methods described herein reduce the subject's risk of relapse or the severity of relapse.

Without wishing to be bound by any particular theory, some cancers, including hematopoietic malignancies, are thought to relapse after an initial period of responsiveness to a therapy due to mechanisms such as antigen loss/antigen escape or lineage switch. In general, antigen loss/antigen escape results in relapse with a phenotypically similar hematopoietic malignancy characterized by cells that lack surface expression of the antigen targeted by the previous therapy (e.g., immunotherapeutic agent) such that the cells are no longer targeted by the previous therapy. In contrast, lineage switch presents as a genetically related but phenotypically different malignancy in which the cells lack surface expression of the antigen targeted by the previous therapy (e.g., immunotherapeutic agent) such that the cells are no longer targeted by the previous therapy. See, e.g., Brown et al. Nature Reviews Immunology (2019) 19:73-74; Majzner et al. Cancer Discovery (2018) 8(10).

Antigen loss/antigen escape in which the target antigen is no longer present on the target cells (e.g., cells of the hematopoietic malignancy) frequently occurs as a result of genetic mutation and/or enrichment of cells that express a variant of the antigen (e.g., lineage-specific cell-surface antigen) that is not targeted by the immunotherapeutic agent (e.g., cytotoxic agent). In some embodiments, the hematopoietic malignancy has relapsed due to antigen loss/antigen escape. In some embodiments, the target cells have lost the targeted epitope (e.g., of a lineage-specific cell-surface antigen) or have reduced expression of the antigen (e.g., lineage-specific cell-surface antigen) such that the targeted epitope is not recognized by the immunotherapeutic agent or is not sufficient to induce cytotoxicity. In some embodiments, the hematopoietic malignancy has relapsed due to lineage switch.

In some embodiments, the methods described herein reduce or avoid relapse of a hematopoietic malignancy by targeting more than one antigen (e.g., more than one lineage-specific cell-surface antigen). In some embodiments, the populations of genetically engineered hematopoietic cells express mutants of more than one lineage-specific surface antigens such that the mutated lineage-specific surface antigens are not targeted by an immunotherapeutic agent(s).

In some embodiments, a cancer treated with the methods herein comprises a first sub-population of cancer cells and a second sub-population of cancer cells. One of the sub-populations may be cancer stem cells. One of the sub-populations may be cancer bulk cells. One of the sub-populations may have one or more (e.g., at least 2, 3, 4, 5, or all) markers of differentiated hematopoietic cells. One of the sub-populations may have one or more (e.g., at least 2, 3, 4, 5, or all) markers of earlier lineage cells, e.g., HSCs or HPCs.

Markers characteristic of different sub-populations of cancer cells (e.g., cancer stem cells and cancer bulk cells) are described, e.g., in van Galen et al. Cell 176, 1-17, Mar. 7, 2019, which is herein incorporated by reference in its entirety. For instance, in some embodiments, the first sub-population of cancer cells comprises primitive AML cells and/or the second sub-population of cancer cells comprises differentiated AML cells (e.g., differentiated monocyte-like AML cells). In some embodiments, a primitive AML cells expresses stemness genes (e.g., as described in van Galen et al., supra) and/or myeloid priming genes (e.g., as described in van Galen et al., supra). In some embodiments, a differentiated monocyte-like AML cell expresses immunomodulatorv genes (e.g., as described in van Galen et al., supra). In some embodiments, one or more of the sub-populations of cancer cells are chosen from: HSC-like, progenitor-like, GMP-like, promonocyte-like, monocyte-like, or conventional dendritic cell (cDC)-like, e.g., as described in van Galen et al., supra.

Any of the immune cells expressing chimeric receptors described herein may be administered in a pharmaceutically acceptable carrier or excipient as a pharmaceutical composition.

The phrase “pharmaceutically acceptable,” as used in connection with compositions and/or cells of the present disclosure, refers to molecular entities and other ingredients of such compositions that are physiologically tolerable and do not typically produce untoward reactions when administered to a mammal (e.g., a human). Preferably, as used herein, the term “pharmaceutically acceptable” means approved by a regulatory agency of the Federal or a state government or listed in the U.S. Pharmacopeia or other generally recognized pharmacopeia for use in mammals, and more particularly in humans. “Acceptable” means that the carrier is compatible with the active ingredient of the composition (e.g., the nucleic acids, vectors, cells, or therapeutic antibodies) and does not negatively affect the subject to which the composition(s) are administered. Any of the pharmaceutical compositions and/or cells to be used in the present methods can comprise pharmaceutically acceptable carriers, excipients, or stabilizers in the form of lyophilized formations or aqueous solutions.

Pharmaceutically acceptable carriers, including buffers, are well known in the art, and may comprise phosphate, citrate, and other organic acids; antioxidants including ascorbic acid and methionine; preservatives, low molecular weight polypeptides; proteins, such as serum albumin, gelatin, or immunoglobulins; amino acids; hydrophobic polymers; monosaccharides: disaccharides; and other carbohydrates; metal complexes; and/or non-ionic surfactants. See, e.g. Remington: The Science and Practice of Pharmacy 20th Ed. (2000) Lippincott Williams and Wilkins, Ed. K. E. Hoover.

Kits for Therapeutic Uses

Also within the scope of the present disclosure are kits for use in treating hematopoietic malignancy. Such a kit may comprise the genetically engineered hematopoietic cells such as HSCs, and optionally one or more cytotoxic agents targeting lineage-specific cell-surface antigens, the genes of which are edited in the hematopoietic cells. Such kits may include a container comprising a first pharmaceutical composition that comprises any of the genetically engineered hematopoietic cells as described herein, and optionally one or more additional containers comprising one or more cytotoxic agents (e.g., immune cells expressing chimeric receptors described herein) targeting the lineage-specific cell-surface antigens as also described herein.

In some embodiments, the kit can comprise instructions for use in any of the methods described herein. The included instructions can comprise a description of administration of the genetically engineered hematopoietic cells and optionally descriptions of administration of the one or more cytotoxic agents to a subject to achieve the intended activity in a subject. The kit may further comprise a description of selecting a subject suitable for treatment based on identifying whether the subject is in need of the treatment. In some embodiments, the instructions comprise a description of administering the genetically engineered hematopoietic cells and optionally the one or more cytotoxic agents to a subject who is in need of the treatment.

The instructions relating to the use of the genetically engineered hematopoietic cells and optionally the cytotoxic agents described herein generally include information as to dosage, dosing schedule, and route of administration for the intended treatment. The containers may be unit doses, bulk packages (e.g., multi-dose packages) or sub-unit doses. Instructions supplied in the kits of the disclosure are typically written instructions on a label or package insert. The label or package insert indicates that the pharmaceutical compositions are used for treating, delaying the onset, and/or alleviating a disease or disorder in a subject.

The kits provided herein are in suitable packaging. Suitable packaging includes, but is not limited to, vials, bottles, jars, flexible packaging, and the like. Also contemplated are packages for use in combination with a specific device, such as an inhaler, nasal administration device, or an infusion device. A kit may have a sterile access port (for example, the container may be an intravenous solution bag or a vial having a stopper pierceable by a hypodermic injection needle). The container may also have a sterile access port. At least one active agent in the pharmaceutical composition is a chimeric receptor variants as described herein.

Kits optionally may provide additional components such as buffers and interpretive information. Normally, the kit comprises a container and a label or package insert(s) on or associated with the container. In some embodiment, the disclosure provides articles of manufacture comprising contents of the kits described above.

General Techniques

The practice of the present disclosure will employ, unless otherwise indicated, conventional techniques of molecular biology (including recombinant techniques), microbiology, cell biology, biochemistry, and immunology, which are within the skill of the art. Such techniques are explained fully in the literature, such as Molecular Cloning: A Laboratory Manual, second edition (Sambrook, et al., 1989) Cold Spring Harbor Press; Oligonucleotide Synthesis (M. J. Gait, ed. 1984): Methods in Molecular Biology, Humana Press; Cell Biology: A Laboratory, Notebook (J. E. Cellis, ed., 1989) Academic Press: Animal Cell Culture (R. I. Freshney, ed. 1987); Introuction to Cell and Tissue Culture (J. P. Mather and P. E. Roberts, 1998) Plenum Press: Cell and Tissue Culture: Laboratory Procedures (A. Doyle, J. B. Griffiths, and D. G. Newell, eds. 1993-8) J. Wiley and Sons; Methods in Enzymology (Academic Press, Inc.); Handbook of Experimental Immunology (D. M. Weir and C. C. Blackwell, eds.): Gene Transfer Vectors for Mammalian Cells (J. M. Miller and M. P. Calos, eds., 1987): Current Protocols in Molecular Biology (F. M. Ausubel, et al. eds. 1987); PCR: The Polymerase Chain Reaction, (Mullis, et al., eds. 1994); Current Protocols in Immunology (J. E. Coligan et al., eds., 1991): Short Protocols in Molecular Biology (Wiley and Sons, 1999): Immunobiology (C. A. Janeway and P. Travers, 1997): Antibodies (P. Finch, 1997); Antibodies: a practice approach (D. Catty, ed., IRL Press, 1988-1989); Monoclonal antibodies: a practical approach (P. Shepherd and C. Dean, eds., Oxford University Press, 2000): Using antibodies: a laboratory manual (E. Harlow and D. Lane (Cold Spring Harbor Laboratory Press, 1999); The Antibodies (M. Zanetti and J. D. Capra, eds. Harwood Academic Publishers, 1995); DNA Cloning: A practical Approach, Volumes I and II (D. N. Glover ed. 1985); Nucleic Acid Hybridization (B. D. Haines & S. J. Higgins eds. (1985»; Transcription and Translation (B. D. Haines & S. J. Higgins, eds. (1984»; Animal Cell Culture (R. I. Freshney, ed. (1986»; Immobilized Cells and Enzymes (IRL Press, (1986»; and B. Perbal, A practical Guide To Molecular Cloning (1984); F. M. Ausubel et al. (eds.).

Without further elaboration, it is believed that one skilled in the art can, based on the above description, utilize the present invention to its fullest extent. The following specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever. All publications cited herein are incorporated by reference for the purposes or subject matter referenced herein.

Example 1: Deletion Exon 2 of CD19 Via CRISPR/Cas9-Mediated Gene Editing and Characterization of Cells Expressing Exon 2-Deleted CD19

This Example reports genetic engineering of CD19 genes via CRISPR/Cas9 in cells to produce edited cells expressing mutated CD19, in which the fragment encoded by exon 2 is deleted (CD19ex2), and in vitro and in vivo characterization of such edited cells. See also above disclosures for exemplary exon-2 deleted CD19 gene products.

Materials and Methods

Design of sgRNA Constructs

All sgRNAs were designed by manual inspection for the SpCas9 PAM (5′-NGG-3′) with close proximity to the target region and prioritized according to predicted specificity by minimizing potential off-target sites in the human genome with an online search algorithm (Benchling, Doench et al 2016, Hsu et al 2013). All designed synthetic sgRNAs were purchased from Synthego with chemically modified nucleotides at the three terminal positions at both the 5′ and 3′ ends. Modified nucleotides contained 2′-O-methyl-3′-phosphorothioate (abbreviated as “ms”) and the ms-sgRNAs were HPLC-purified. Cas9 protein was purchased from Synthego (FIGS. 5-8B) and Aldervon (FIGS. 9A, 9B, 10A-10D, 14A-14D, 17, 18A and 18B).

Cell Maintenance and Electroporation of Immortalized Human Cell Lines

K562 human leukemia cell lines were obtained from American Type Culture Collection (ATCC) and maintained in DMEM+10% FBS and maintained at 37° C. at 5% CO2. K562 cells were edited by electroporation of the Cas9 ribonucleoprotein (RNP) using the Lonza Nucleofector (program SF-220) and the Human P3 Cell Nucleofection Kit (VPA-1002, Lonza). Raji-Fluc-GFP cells were purchased from Capital Biosciences and maintained in RPMI+10% FBS+1% Glutamine at 37° C. at 5% CO2. Raji-Fluc-GFP cells were edited by electroporation of RNP using the Lonza Nucleofector (program DS-104) and SG Cell line 4D-Nucleofector X Kit S (V4XC-3032, Lonza). Cas9 RNP was made by incubating protein with ms-sgRNA at a molar ratio of 1:9 (20:180 pmol) at 25° C. for 10 minutes immediately before electroporation. After electroporation, cells were incubated for 10 minutes in the cuvette, transferred to 1 mL of the above medium, and cultured for 24-72 hrs for downstream analysis.

Editing in Primary Human CD34+ HSCs

Frozen CD34+ HSCs derived from mobilized peripheral blood were purchased from AllCells and thawed according to manufacturer's instructions. Frozen CD34+ HSCs derived from cord blood were either purchased frozen from AllCells or Stemcell and thawed and maintained according to manufacturer's instructions. To edit HSCs, ˜1e6 HSCs were thawed and cultured in StemSpan SFEM medium supplemented with StemSpan CC 110 cocktail (StemCell Technologies) for 24 h before electroporation with RNP. To electroporate HSCs, 1.5e5 were pelleted and resuspended in 20 μL Lonza P3 solution, and mixed with 10 uL Cas9 RNP as described above. CD34+ HSCs were electroporated using the Lonza Nucleofector 2 (program DU-100) and the Human P3 Cell Nucleofection Kit (VPA-1002, Lonza).

Genomic DNA Analysis

For all genomic analysis, DNA was harvested from cells using the Qiagen DNeasy kit. For T7E1 assays, PCR was performed with primers flanking the CRISPR cut sites. Products were purified by PCR purification (Qiagen) and 200 ng was denatured and re-annealed in a thermocycler and digested with T7 Endonuclease I (New England Biolabs) according to manufacturer's protocol. Digested DNA were electrophoresed in a 1% agarose gel and viewed on a BioRad ChemiDoc imager. Band intensities were analyzed using the Image Lab Software (Bio-Rad) and allele modification frequencies (INDEL) were calculated with the formula: 100×(1−(1−fraction cleaved){circumflex over ( )}0.5). For analyzing allele modification frequencies using TIDE (Tracking of In/dels by Decomposition), the purified PCR products were Sanger-sequenced (Eton) using both PCR primers and each sequence chromatogram was analyzed with the online TIDE software (Deskgen). Analyses were performed using a reference sequence from a mock-transfected (Cas9 protein only) sample. Parameters were set to the default maximum indel size of 10 nucleotides and the decomposition window to cover the largest possible window with high quality traces. All TIDE analyses below the detection sensitivity of 3.5% were set to 0%.

To determine the extent genomic deletion with dual ms-sgRNAs, endpoint PCR was performed with primers flanking CRISPR cut sites that amplify an 804 bp region. PCR products were electrophoresed in a 1% agarose gel and viewed on a BioRad ChemiDoc imager to observe the intact parental band and the expected smaller (400-600 bp depending on ms-sgRNA combination) deletion product. Band intensities were analyzed using the Image Lab Software (Bio-Rad) and percent deletions were calculated with the formula: 100×fraction cleaved). Gel bands were extracted with a gel extraction kit (Qiagen) and further purified by PCR purification (Qiagen) for Sanger sequencing (Eton Bioscience).

Flow Cytometry and FACS Analysis

Raji-fluc-GFP cells nucleofected with RNP as described above were maintained in cell culture for 48 hrs. Live cells were stained with PE-conjugated CD19 antibody (IM1285U; Beckman Coulter) and analyzed sorted on a BD FACS Aria by expression of CD19. CD34+ HSCs were stained for CD33 using an anti-CD33 antibody (P67.7) and analyzed by flow cytometry on the Attune N×T flow cytometer (Life Technologies).

CAR-T Cell Cytotoxicity Assays

CD19-directed CAR-T cells (CART 19) were generated by transduction of CART19-expressing lentivirus into CD4+ and CD8+ T cells from healthy human donors. CART19 construct contains a CD19-recognizing domain (single chain variable fragment derived from FMC63 monoclonal antibody), a costimulatory domain derived from CD28, and the CD3 zeta domain. The cytotoxicity of CART19 was assessed by flow cytometry-based assay. Raji-fluc-GFP cells stained with CellTrace Violet dye served as target cells. T cells not transduced with CART19 construct were used as a negative control for the cytotoxicity assay. The effector (E) and tumor target (T) cells were co-cultured at the indicated ET ratios (10:1, 3:1, 0:1), with 1×10⁴ target cells in a total volume of 200 μl per well in CTS OpTmizer-based serum free medium. After 20 hours of incubation, cells were stained for Propidium Iodide and analyzed by Attune N×T flow cytometer (Life Technologies). Live target cells were gated as Propidium Iodide-negative and CellTrace Violet-positive. Cytotoxicity was calculated as (1-(Live target cell fraction in CART19 group)/(Live target cell fraction in negative control group))×100%.

In Vivo Engraftment Experiments

For CD19 in vivo engraftment experiments, cells are engrafted into NOD scid gamma mice (NSG™ mice: The Jackson Laboratory). For CD33 in vivo engraftment experiments, cells are engrafted into NSG-SGM3 mice (The Jackson Laboratory).

In Vitro CFU Assay

1500 sorted CD34+ HSPCs were plated in 1.5 ml of methylcellulose (MethoCult™ H4034 Optimum, Stem Cell Technologies) on a 35 mm cell culture dish and cultured for two weeks at 37° C. in a 5% CO2 incubator. Colonies were then counted and scored based on morphological appearance.

Results (i) Selection of RNAs

Exon 2 of CD19 was targeted for CRISPR/Cas9-mediated genomic deletion as exemplified in FIG. 4. A pair of sgRNAs, one sgRNA targeting intron 1 and one sgRNA targeting intron 2, leads to simultaneous generation of DNA double stranded breaks (DSBs) by Cas9 and excision of the region including complete loss of exon 2 of CD19. The ends distal to the cut site are repaired through ligation of introns 1 and 2 via non-homologous end joining (NHEJ). Transcription of the modified CD19 gene results in expression of a CD19 variant lacking exon 2 (“CD19exon2 deletion”) via exon 2 skipping during RNA splicing.

A panel of sgRNAs targeting introns 1 and 2 was designed by manual inspection for the SpCas9 PAM (5′-NGG-3′) with close proximity to CD19 exon 2 and prioritized according to predicted specificity by maximizing on-target and minimizing potential off-target sites in the human genome with an online search algorithm (Benchling, Doench et al (2016); Hsu et al (2013)) (Table 3). Exon 4 of CD19 may also be targeted for CRISPR/Cas9-mediated genomic deletion, for example using sgRNA-23 and sgRNA-24 (Table 3). For each of the example CD19 sgRNAs, the sequence targets CD19 and the Cas type is SpCas9.

TABLE 3 CD19 sgRNA panel On Target Off Target (Doench et (Hsu et al Name sgRNA Sequence Location Strand PAM al 2016)¹ 2013)¹ CD19_sgRNA GAGGCTGGAAACTTGAGTTG Intron 1  1 TGG 57 67 −1 (SEQ ID NO: 14) CD19_sgRNA GAGGGTAAGTTACTCAGCCA Intron 1 −1 AGG 68 60 −3 (SEQ ID NO: 15) CD19_sgRNA AAATTCAGGAAAGGGTTGGA Intron 1  1 AGG 53 62 −4 (SEQ ID NO: 16) CD19_sgRNA AAGGGTTGGAAGGACTCTGC Intron 1  1 CGG 60 64 −5 (SEQ ID NO: 17) CD19_sgRNA AGCAGAGGACTCCAAAAGCT Intron 1 −1 GGG 62 59 −6 (SEQ ID NO: 18) CD19_sgRNA CACACCAGGTTATAGAGCAG Intron 1 −1 AGG 63 67 −7 (SEQ ID NO: 19) CD19_sgRNA CTGCTCTATAACCTGGTGTG Intron 1  1 AGG 63 67 −8 (SEQ ID NO: 20) CD19_sgRNA ACCTGGTGTGAGGAGTCGGG Intron 1  1 GGG 58 69 −9 (SEQ ID NO: 21) CD19_sgRNA CACAGCGTTATCTCCCTCTG Exon 2 −1 TGG 68 69 −10 (SEQ ID NO: 22) CD19_sgRNA CGGACCTCTTCTGTCCATGG Intron 2 −1 TGG 65 65 −13 (SEQ ID NO: 23) CD19_sgRNA CCATGGACAGAAGAGGTCCG Intron 2  1 CGG 72 65 −14 (SEQ ID NO: 24) CD19_sgRNA GGGCGAAACTCGGAGCTAGG Intron 2  1 TGG 80 65 −15 (SEQ ID NO: 25) CD19_sgRNA GCTAGGTGGGCAGACTCCTG Intron 2  1 GGG 59 60 −16 (SEQ ID NO: 26) CD19_sgRNA GGAACCTCTAGTGGTGAAGG Exon 1 TGG −18 (SEQ ID NO: 69) CD19_sgRNA CACAGCGTTATCTCCCTCTG Exon 2 GGT −19 (SEQ ID NO: 70) CD19_sRNA GGACAGGGAGAGATAAGACA Intron 4 AGG −23 (SEQ ID NO: 71) CD19_sgRNA AGGTAGAGTTTCTCTCAACT Intron 4 GGG −24 (SEQ ID NO: 72) ¹On and Off-target predictions based on the indicated published algorithms. Score is out of 100 and is a prediction of success.

For gene editing, the sgRNAs were modified as described in the Materials and Methods. The modified sgRNAs are denoted with “ms” prefix. The CD19 sgRNAs targeting either intron 1 or 2 were screened in K562 cells, a human leukemic cell line and analyzed by T7E1 assay and TIDE analysis (FIG. 5). Of the 12 ms-sgRNAs assessed, ms-sgRNAs 1, 3-9 target intron 1, ms-sgRNA 10 targets exon 2, and ms-sgRNA 14-16 target intron 2. The percent INDEL for ms-sgRNA-1 was not calculated for this sample because the size-change between edited and unedited bands could not be accurately distinguished using the current set of PCR primers.

Pairs of ms-sgRNAs were used to delete exon 2 of CD19 in K562 cells, and a PCR-based assay was used to detect CRISPR/Cas9-mediated genomic deletion of CD19 exon 2 (FIG. 6). The combined activity of ms-sgRNAs targeting intron 1 (ms-sgRNAs 3, 4, 5, 6, 9) were screened in combination with ms-sgRNAs targeting intron 2 (ms-sgRNAs 14, 15, 16) to generate genomic deletions. PCR across the genomic deletion region shows the smaller deletion PCR product (400-560 bp) compared to the larger parental band (801 bp). The editing efficiency was quantified as percent deletion by end-point PCR (FIG. 6, panel C).

(ii) In Vitro Characterization of CD34 Cells Expressing Exon 2-Deleted CD19

The CD19 sgRNAs targeting either intron 1 or 2 were screened in CD34⁺ HSCs (FIGS. 7 and 9). Pairs of ms-gRNAs were used to delete exon 2 of CD19 in CD34⁺ HSCs. The combined activity of ms-sgRNAs targeting intron 1 (ms-sgRNAs 4, 6, 9) were screened in combination with ms-sgRNAs targeting intron 2 (ms-gRNAs 14, 15, 16) to generate genomic deletions (FIGS. 8A and 8B). PCR across the genomic deletion region shows the smaller deletion PCR product compared to the larger parental band. The editing efficiency was quantified a percent deletion by end-point PCR.

Additional pairs of ms-gRNAs were used to delete exon 2 of CD19 in CD34⁺ HSCs. The combined us of ms-sgRNAs targeting intron 1 (ms-sgRNAs 1, 6, 7) in combination with ms-sgRNAs targeting intron 2 (ms-gRNAs 14, 15, 16) were found to efficiently generate genomic deletions of exon 2 (FIG. 10A and FIG. 10B).

PCR across the genomic deletion region shows the smaller deletion PCR product compared to the larger parental band. The results show high efficiency generation of HSCs expression CD19ex2 upon CRISPR editing using the gRNA6/gRNA14 pair. FIG. 10C. In vitro CFU assay shows that CD19ex2 HSCs did not affect in vitro differentiation. FIG. 10D. For the CFU assay, 1500 sorted CD34+ HSPCs were plated in 1.5 ml of methylcellulose (MethoCult™ H4034 Optimum, Stem Cell Technologies) on a 35 mm cell culture dish and cultured for two weeks at 37° C. in a 5% CO2 incubator. Colonies were then counted and scored based on morphological appearance

(iii) Characterization of Raji B-Cell Lymphoma Cells Expressing Exon 2-Deleted CD19

The CD19 sgRNAs targeting either intron 1 or 2 were also screened in Raji B-cell lymphoma cells HSCs. Pairs of ms-gRNAs were used to delete exon 2 of CD19 (CD19ex2) in Raji B-cell lymphoma cells. The combined activity of ms-sgRNAs targeting intron 1 (ms-sgRNA 6) were used in combination with ms-sgRNAs targeting intron 2 (ms-gRNA 14) to generate genomic deletions. FIG. 11A. PCR across the genomic deletion region shows the smaller deletion PCR product compared to the larger parental band. The ex2 small deletion band represents a product resulting from an alternative DNA repair event after Cas9 cleavage. The ex2 small deletion sequence encodes the same CD19 mutant with deletion of the fragment encoded by exon 2. The editing efficiency was quantified a percent deletion by end-point PCR. FIG. 11B.

Protein analysis of clonal lymphoma cells expression exon 2-deleted CD19 (CD19ex2) was analyzed by both Western Blot using an antibody that recognizes the C-terminus of CD19 and Flow Cytometry using the FMC63 anti-CD19 antibody (recognizing the CD19 region encoded by exon 2) or a polyclonal anti-CD19 antibody. Expression levels of exon 2-deleted CD19 (CD19ex2) in clonal lymphoma cells was analyzed by both Western Blot using an antibody that recognizes the C-terminus of CD19 (#3574 Rabbit anti-human CD19 Pab, Cell Signaling Technology) of whole cell lysates or flow cytometry using the FMC63 anti-CD19 antibody (FMC63 R-PE Mouse anti-human CD19 Mab, EMD Millipore) that recognizes the CD19 region encoded by exon 2. A polyclonal anti-CD19 antibody (#3574 Rabbit anti-human CD19 Pab, Cell Signaling Technology) was used to identify intracellular CD19 by intracellular staining and flow cytometry.

Expression of exon 2-deleted CD19 was observed in Raji B-cells with one or both chromosomes edited as detected by Western Blot. FIG. 11C. Similarly, surface expression and intracellular presence of exon 2-deleted CD19 were also detected in Raji B-cells by Flow Cytometry. FIG. 11D.

Further, growth and viability of Raji B-cells expressing CD19exon2 were analyzed. Human lymphoma cell line, Raji, was obtained from the American Type Culture Collection (ATCC). Raji cells were cultured in RPMI-1640 media (ATCC) supplemented with 10% heat-inactivated HyClone Fetal Bovine Serum (GE Healthcare). Cell viability and live cell number were measured by an automated cell counter, Cellmoter (Nexcelom). As shown in FIG. 11E, cells expressing CD19exon2 did not show defects in proliferation (left panel) and viability (right panel).

(iv) Engraftment of CD19ex2 Hematopoietic Stem Cells (HSCs) in a Humanized Mouse Model

An exemplary flowchart for generating HSCs expression CD19ex2 and characterization of the in vivo differentiation of the HSCs in a humanized mouse model (e.g., NSG mice) is provided in FIG. 12A. In some examples, CAR-T treatment can be performed at 14w after HSPC engraftment. The NSG mice can be assigned the four groups shown in Table 4 below:

TABLE 4 In vivo characterization groups Group Condition Value Endpoint Expectation 1 RNP Control + Mock CAR-T EP control Functional B Cell 2 CD19ex2 + Mock CAR-T Target Functional FL/CD19ex2 B Cell 3 RNP control + CART19 CAR-T selectivity B-Cell Loss 4 CD19ex2 + CART19 CAR-T selectivity Retained B-Cell

CD34⁺ HSC cells expressing CD19ex2 were produced using the combination of ms-sgRNAs targeting intron 1 (ms-sgRNA 6) and ms-sgRNAs targeting intron 2 (ms-gRNA 14) to generate genomic deletions as described above. See also the Materials and Methods. Samples were split into two fractions: 2% of cells were characterized in vitro and the remaining fraction is engraftment into 6-8 week old NOD scid gamma mice (NOD.Cg-Prkdc^(scid)Il2rg^(tmlWjl)/SzJ (NSG™ mice), a humanized mouse model. The Jackson Laboratory. The in vitro fraction was characterized by colony forming unit (CFU) assay and genotyping as described above.

The in vivo fraction was administered to irradiated NSG™ mice. Blood samples can be obtained from the mice at various time points (e.g., 4 weeks, 8 weeks, 12 weeks) and analyzed by genotyping and to assess the percentage human CD45+ cells. At 16 weeks, the mice can be sacrificed and peripheral blood, bone marrow, and spleens were harvested for analysis. The primary endpoint is percent engraftment, which can be assessed by genotyping and flow cytometric analysis (e.g., mouse vs human CD45, CD20/CD19, CD19 deficient in exon 2, Cd34, CD33, CD3). A secondary endpoint can be expression of CD19 that is deficient in exon 2 by Western blotting and/or qRT-PCR.

Percentage of hCD45+ cells in peripheral blood collected from the HSC-treated mice was determined by flow cytometry and the results are provided in FIG. 12B. The edited HSCs expressing CD19ex2 showed efficient engraftment in the NSG mice at week 4, 9 and 12 at levels substantially the same as the control HSC cells.

The levels of CD45+/CD20+ cells, representing differentiated B cells, in peripheral blood collected from the NSG mice were measured at week 9 after infusion of RNP HSCs or CD19ex2 HSCs. As shown in FIG. 12C, the edited cells (CD19ex2 HSCs) showed a significantly higher level of B cell differentiation than the unedited cells (RNP HSCs) at 9 and 12 weeks.

(v) In Vivo Raji Tumor Model

An in vivo Raji tumor model can be used to assay the efficacy of any of the treatment methods described herein. Raji-fluc-GFP cells expressing endogenous CD19 deficient in exon 2 (CD19exon2 delete) were generated ex vivo as described in the Materials and Methods. Following enrichment of edited cells, samples are split into two fractions: one fraction is characterized in vitro and the remaining fraction is xenografted into 6-8 week old NSG mice (FIG. 13).

The in vitro fraction is characterized by cytotoxicity and molecular assays as described in the Materials and Methods. The in vivo fraction is assessed for efficacy and selectivity of CART19 in Burkett Lymphoma mouse model and assayed by the indicated assays and as described in Materials and Methods. The groups of mice are shown in Table 5. Briefly, one week following injection of the Raji-fluc-GFP cells expressing endogenous CD19 deficient in exon 2, the mice are infused CART19 cells. The mice are assessed at various time points (e.g., 6 days, 12 days, 18 days, 35 days) by in vivo imaging system (IVIS) to determine the abundance of Raji cells (CD19/CD19ex2). Blood samples are also obtained from the mice to quantify the number of CART 19 cells.

TABLE 5 In vivo characterization groups Group Condition CART19 # Mice 1 Untreated control − 4 2 Untreated control + 10 3 Raji Fluc GFP; CD19+/+ − 10 4 Raji Fluc GFP; CD19+/+ + 10 5 Raji Fluc GFP; CD19exon2DEL − 10 6 Raji Fluc GFP; CD19exon2DEL + 10

The primary endpoint of treatment efficacy is assessed, for example, by survival, tumor burden volume, and tumor burden by IVIS imaging. The primary endpoint of treatment selectivity is assessed, for example, by determining persistence of Raji-GFP cells. Secondary endpoints for CART19 therapy include pharmacokinetics and tumor infiltration, and secondary endpoints for CD19 include expression of CD19 that is deficient in exon 2.

It is expected that Raji cells expressing exon 2 of CD19 will be killed by the CART19 cells, whereas the Raji cells that have been manipulated to delete exon 2 of CD19 will survive and evade CART killing.

(vi) Generation of Raji-Fluc-GFP Cells Lines Deficient in CD19 Exon 2

Raji-fluc-GFP cell lines were transfected with pairs of ms-sgRNAs and assayed for CD19 expression by fluorescence-activated cell sorting (FACS). Cells were gated into three populations based on relative CD19 expression: “hi” (high), “int” (intermediate), and “lo” (low) (FIG. 14A). Parental Raji cells and Raj-fluc-GFP nucleofected with Cas9 only were included as controls. The percentage of live cells in each condition was quantified (FIG. 14B). PCR was also performed across the genomic deletion region of cells in each condition showing the smaller deletion PCR product compared to the larger parental band (FIG. 14C). The percentage CD19 exon 2 in the bulk population was also assayed by end-point PCR in each condition (FIG. 14D), indicating there was a higher percentage of cells with the CD19 exon 2 deletion in the CD19 “int” and CD19 “lo” cell populations.

(vii) CART Cytotoxicity

CD19-directed CAR-T cells (CART 19) were generated as described in the Materials and Methods and incubated with Raji-fluc-GFP cells. Following 20 hours of incubation, cytotoxicity was assessed by flow cytometry. FIG. 15A and FIG. 15B shows there was reduced specific lysis of CD19 “low” Raji cells as compared to CD19 “hi” populations.

As shown in FIGS. 14A-14D, the Raji “hi” population is genotypically mixed population of cells. Single cells may be enriched to analyze clonal populations as well as unedited parental populations. The control CD19-hi population is a mixed genotype (20-40% CD19exon2 delete), and enhanced killing is expected with wild-type control populations.

(viii) In Vivo Efficacy and Selectivity

FIG. 16 outlines a comprehensive in vivo model assessing efficacy and selectivity of CART therapy paired with edited HSCs. Briefly, HSCs deficient in exon 2 of CD19 (CD19ex2delete) are prepared. Groups of mice are administered either control (unedited) HSCs or HSCs deficient in exon 2 of CD19. After four weeks, the mice are administered Raji Burkitt's lymphoma cells, followed by CART19 cells one week later. The mice are assessed weekly by IVIS imaging, and blood samples are obtained every four weeks. After 12 weeks, the mice are sacrificed and peripheral blood, bone marrow, and spleens are harvested for analysis.

Example 2: Deletion Exon 2 of CD33 Via CRISPR/Cas9-Mediated Gene Editing and Characterization of Cells Expressing Exon 2-Deleted CD33

This Example reports genetic engineering of CD33 genes via CRISPR:Cas9 in cells to produce edited cells expressing mutated CD33, in which the fragment encoded by exon 2 is deleted (CD33ex2), and in vitro and in vivo characterization of such edited cells using assays described in Example 1 above or known in the art. See also above disclosures for exemplary exon-2 deleted CD33 gene products.

(i) Selection of gRNAs

As shown in FIG. 17, the Cas9 nuclease is targeted to introns 1 and 2 of CD33 by two sgRNAs. Simultaneous generation of DNA double stranded breaks (DSBs) by Cas9 leads to excision of the region including complete loss of exon 2. The ends distal to the cut site are repaired through ligation of introns 1 and 2 via non-homologous end joining (NHEJ) with the repaired junction indicated by the triangle. Transcription of the modified genome results in expression of CD33m isoform.

A panel of ms-sgRNAs was designed by manual inspection for the SpCas9 PAM (5′-NGG-3′) with close proximity to CD33 exon 2 and prioritized according to predicted specificity by minimizing potential off-target sites in the human genome with an online search algorithm (Benchling, Doench et al (2016); Hsu et al (2013)) (Table 6). A subset of ms-sgRNAs targeting either intron 1 or 2 was then selected based on in vitro gene editing efficiency. Each of the sgRNAs target human CD33 and use Cas9 type SpCas9.

TABLE 6 CD33 sgRNA panel On Target Off Target (Doench et al (Hsu et al Name sgRNA Sequence PAM Location 2016)¹ 2013)¹ CD33_sgRNA GCTGTGGGGAGAGGGGTTGT CGG Intron 1 39 29 −1 (SEQ ID NO: 27) CD33_sgRNA CTGTGGGGAGAGGGGTTGTC GGG Intron 1 46 35 −2 (SEQ ID NO: 28) CD33_sgRNA TGGGGAAACGAGGGTCAGCT CGG Intron 1 60 29 −3 (SEQ ID NO: 29) CD33_sgRNA GGGCCCCTGTGGGGAAACGA GGG Intron 1 65 40 −4 (SEQ ID NO: 30) CD33_sgRNA AGGGCCCCTGTGGGGAAACG AGG Intron 1 50 36 −5 (SEQ ID NO: 31) CD33_sgRNA GCTGACCCTCGTTTCCCCAC AGG Intron 1 47 31 −6 (SEQ ID NO: 32) CD33_sgRNA CTGACCCTCGTTTCCCCACA GGG Intron 1 52 27 −7 (SEQ ID NO: 33) CD33_sgRNA TGACCCTCGTTTCCCCACAG GGG Intron 1 71 29 −8 (SEQ ID NO: 34) CD33_sgRNA CCATAGCCAGGGCCCCTGTG GGG Intron 1 61 24 −9 (SEQ ID NO: 35) CD33_sgRNA GCATGTGACAGGTGAGGCAC AGG Intron 2 56 36 −10 (SEQ ID NO: 36) CD33sgRNA TGAGGCACAGGCTTCAGAAG TGG Intron 2 55 32 −11 (SEQ ID NO: 37) CD33_sgRNA AGGCTTCAGAAGTGGCCGCA AGG Intron 2 54 39 −12 (SEQ ID NO: 38) CD33_sgRNA GGCTTCAGAAGTGGCCGCAA GGG Intron 2 58 44 −13 (SEQ ID NO: 39) CD33_sgRNA GTACCCATGAACTTCCCTTG CGG Intron 2 75 40 −14 (SEQ ID NO: 40) CD33_sgRNA GTGGCCGCAAGGGAAGTTCA TGG Intron 2 63 42 −15 (SEQ ID NO: 41) CD33_sgRNA TGGCCGCAAGGGAAGTTCAT GGG Intron 2 53 43 −16 (SEQ ID NO: 42) CD33_sgRNA GGAAGTTCATGGGTACTGCA GGG Intron 2 66 42 −17 (SEQ ID NO: 43) CD33_sgRNA TTCATGGGTACTGCAGGGCA GGG Intron 2 59 32 −18 (SEQ ID NO: 44) CD33_sgRNA CTAAACCCCTCCCAGTACCA GGG Intron 2 61 40 −19 (SEQ ID NO: 45) CD33_sgRNA CACTCACCTGCCCACAGCAG GGG Intron 1 56 23 −20 (SEQ ID NO: 46) CD33_sgRNA CCCTGCTGTGGGCAGGTGAG TGG Intron 1 44 20 −21 (SEQ ID NO: 47) CD33_sgRNA TGGGCAGGTGAGTGGCTGTG GGG Intron 1 61 26 −22 (SEQ ID NO: 48) CD33_sgRNA GGTGAGTGGCTGTGGGGAGA GGG Intron 1 42 24 −23 (SEQ ID NO: 49) CD33_sgRNA GTGAGTGGCTGTGGGGAGAG GGG Intron 1 49 20 −24 (SEQ ID NO: 50) ¹On and Off-target predictions based on the indicated published algorithms. Score is out of 100 and is a prediction of success.

The CD33 ms-sgRNAs targeting introns 1 or 2 were screened in primary CD34's HSCs by TIDE assay (FIGS. 17A and 17B).

Pairs of ms-gRNAs were used tested in CD34+ HSCs (FIGS. 18B and 18C; FIG. 27). Efficient deletion of exons 2 and 3, leading to knock-out of CD33, was observed using control sgRNAs targeting exons 2 and 3 (Sg and 811, respectively). A reduction in CD33 containing exon 2 was observed with pairs of sgRNAs targeting introns 1 and 2 (e.g., sgRNAs 17 and 23; sgRNAs 18 and 24).

FIG. 19A shows results from flow cytometry showing CD34+ HSCs, either unedited (left panel, mock) or edited with guide RNAs for KO (producing a full CD33 knockout (middle panel) or edited with guide RNAs 18 and 24 resulting in the expression of mutated CD33 with exon 2-encoded fragment deleted (CD33ex2, right panel). FIG. 19B shows the editing efficiency as determined from the flow cytometric analysis shown in FIG. 19A. The percentage of CD34+CD33ex2 events was determined using deletion PCR containing primers flanking exon 2 (shown in black).

(ii) Genotyping and In Vitro Differentiation of Dual gRNA-Targeted CD33ex2 Cells

CFU assays of cells edited by the pair of gRNA18 and gRNA24, as well as CD33-KO CD34⁺ HSC cells show that both type of cells retain differentiation potential in vitro. FIG. 20A. PCR genotyping of a number of differentiated myeloid cell clones expressing the CD33ex2 mutant show that the pair of gRNA18 and gRNA24 resulted in a mixture of exon 2 deleted CD33 alleles and CD33 knocked-out alleles. FIG. 19B and FIG. 20B. The genotypes and frequencies are provided in Table 7 below

TABLE 7 Genotype and Frequency of Differentiated CD33ex2 Myeloid Cells Genotype Frequency KO/KO 44 of 87 ex2/ex2 16 of 87 ex2/KO 27 of 87

(iii) Generation and Characterization of CD33ex2 in AML Cell Lines

AML cell lines THP1 (monocytic leukemia) and HL-60 (promyeloblast leukemia) were genetically edited via CRISPR/Cas9 using the pair of gRNA18 and gRNA24 to produce cells expressing CD33ex2, which were sorted by flow cytometry. Single cells were expanded to establish clones that express CD33ex2, which were subject to gemtuzumab ozogamicin treatment as disclosed below. Genomic PCR showed that the CD33 exon 2 was deleted either in one CD33 allele or in both alleles. FIG. 21A. FIG. 21B illustrates the PCR primer pairs for detecting total CD33, including both full length (M) and exon 2 deletion (m) and the PCR primer pairs for detecting only CD33m. One clone shows partial deletion in the exon 1 region. The levels of full-length CD33 transcripts and CD33ex2 transcripts were analysed by an RNA analysis and the results are shown in FIG. 21C. Deeper genomic characterization via PCR and sequencing analysis show reproducible repair ligation of intron 1 and intron 2. Depending on the type of IDEL the repair ligation results in either transcripts resulting in CD33ex2 or full CD33 KO. For example, in some cases the INDELS extend into exon 1, resulting in a CD33 KO.

(iv) CD33ex2 Cells are Less Susceptible to Gemtuzumab Ozogamicin (GO) Cytotoxicity

The AML cell clones expressing CD33ex2 were treated with gemtuzumab ozogamicin and the viability of the treated cells was determined. Human AML cell lines, THP-1 and HL-60, were obtained from the American Type Culture Collection (ATCC). THP-1 cells were cultured in RPMI-1640 media (ATCC) supplemented with 10% heat-inactivated HyClone Fetal Bovine Serum (GE Healthcare) and 0.05 mM 2-mercaptoethanol (Sigma-Aldrich). HL-60 cells were cultured in Iscove's Modified Dulbecco's Medium (IMDM, Gibco) supplemented with 20% heat-inactivated HyClone Fetal Bovine Serum (GE Healthcare). For in vitro cytotoxicity assays with AML cell lines, THP-1 and HL-60 cells were incubated with GO in their complete culture media for 72 hours. Increasing concentrations of GO, from 0.1 ng/mL to 10 μg/mL, were used. Cells were plated at 2×104 per well in 96 well plates. Viable cell number was measured with Celltiter Glo (Promega) according to manufacturer's instructions, and luminescence was determined using a GloMax multiplate reader (Promega). IC50 was defined as the concentration of compound needed to yield a 50% reduction in viable cell number compared with no GO treated cells (control=100%). To measure cell death, cells were stained with Annexin V (Invitrogen) and DAPI (Biolegend) for 15 minutes in 1× Annexin Binding Buffer (Invitrogen) at room temperature. Data was acquired on Attune N×T flow cytometer (ThermoFisher Scientific), and analyzed with FlowJo software (TreeStar).

As shown in FIG. 22A, AML cell lines THP-1 and HL-60 are more susceptible to GO cytotoxicity (IC₅₀ 16.3 ng/ml and 35.5 ng/ml, respectively) as compared with Jurkat cells (IC₅₀ 902.7 ng/ml). Edited AML cells expressing CD33ex2 showed lower susceptibility to GO cytotoxicity as compared with the unedited parent cells. FIG. 22B.

Similar results were observed in edited HSPC cells expressing CD33ex2. In one study, the IC₅₀ value of wild-type HSPC was found to be around 93.4 ng/ml, and the IC₅₀ values of HSPC CD33KO and HSPC CD33ex2 were found to be around 248.1 ng/ml and 246.4 ng/ml, respectively.

Wild-type HSC cells (CD33+), CD33 KO HSCs and CD33ex2 HSCs were treated with GO and the surviving cells were cultured in a myeloid culture medium for 30 days after withdrawal of GO treatment. The viability of the surviving cells was determined as described above. Surprisingly, CD33ex2 HSCs showed much higher viability post GO treatment, as compared with wild-type and CD33 KO HSC cells. FIG. 22C.

(i) CD33ex2 Cells are Protected from CART33-Mediated Killing

CD33-directed CAR-T cells (CART33 or CAR1) were generated by transduction of CART33-expressing lentivirus into CD4⁺ and CD8⁺ T cells from healthy human donors. The CART33 construct contains a single chain variable fragment (scFv) that recognizes the fragment of CD33 encoded by exon 2, a hinge domain of CD8α, a transmembrane domain of CD8, a co-stimulatory domain of 4-1BB, and a cytoplasmic signaling domain of CD3ζ.

The cytotoxicity of CART33 was assessed by flow cytometry-based assay. Raji (CD33⁻) cells were used as a negative control for the cytotoxicity assay. The effector (E) and tumor target (T) cells were co-cultured at the indicated ET ratios (5:1 and 1:1), with 1×10⁴ target cells in a total volume of 200 μl per well in CTS OpTmizer-based serum free medium. After 20 hours of incubation, cells were stained for Propidium Iodide and analyzed by Attune N×T flow cytometer (Life Technologies). Live target cells were gated as Propidium Iodide-negative and CellTrace Violet-positive. Cytotoxicity was calculated as (1−(Live target cell fraction in CART19 group)/(Live target cell fraction in negative control group))×100%6.

A high level of cell lysis was observed in CD33′ HL-60 cells (FIG. 23A) and expression of CD33ex2 mutant in HL-60 cells significantly reduced the level of cell lysis (FIG. 23B), similar to HL-60 cells having CD33 knocked-out (FIG. 23C). The comparison results are provided in FIG. 23D.

Example 3: Efficient Multiplex Genomic Editing

Efficient double genomic editing of CD19 and CD33 genes in HSC cells were performed in either NALM-6 cells or in HSCs following conventional methods or those described herein. Table 8 below provides the gRNAs targeting exon 2 of CD19 and exon 3 of CD33.

TABLE 8 Guide RNAs for Double Editing of CD19 and CD33 Loca- Gene gRNA Name gRNA Sequence PAM tion CD19 CD19_gRNA-19 CACAGCGTTATCTCCCTCTG GGT Exon 2 (SEQ ID NO: 66) CD33 CD33_gRNA-37 CCCCAGGACTACTCACTCCT CGG Exon 3 (SEQ ID NO: 67)

Genomic DNA was isolated from bulk-edited cells and TIDE assays were performed to examine genomic editing in NALM-6, HL-60 cells and HSCs. Results are depicted in FIGS. 24A-24D. The results obtained from this study show that ˜70% of the HSCs include mutations in both loci of the CD19 gene and ˜80% of the HSCs include mutations in both loci of the CD33 gene, indicating that at least 50% of the double-edited cells have both edited CD19 gene and edited CD33 gene on at least one chromosome. Similar levels of edited cells were observed in HL-60 cells and Nalm-6 cells.

Example 4: Effect of Editing Multiple Loci on Viability

The effect of genomic editing at multiple loci on cell viability was assessed NALM-6. HL-60 cells and HSCs. Two days before nucleofection, HSPCs were thawed or Nalm-6 or HL-60 cells were passaged. At 24 and 48 hours (day of nucleofection), cells were counted and cell viability was assessed. Nucleofection with CD33_gRNA-37 RNP and CD19_gRNA-19 complexes and was performed according to Materials and Methods described herein. Cells were counted and cell viability was assessed at the indicated timepoints. Results are depicted in FIGS. 25A-25C and indicate that dual Cas9/gRNAs delivery does not impair viability in cell lines. No additional toxicity over single guide RNA was observed in HSCs.

Example 5: Performance of Individual Guides

The efficiency of genomic editing for the individual guide RNAs CD33 sgRNA-18 and CD33 sgRNA-24 was assessed in HL-60 cells. Genomic DNA was isolated from bulk-edited cells and TIDE assays were performed to examine genomic editing. Results are depicted in Table 9.

TABLE 9 Percentage of INDELs resulting from gRNA 18 and gRNA 24 individually Indel in CD33 Guide HL60 cells 3′-sg 18 94% 5′-sg-24 46%

Example 6: Treatment of Hematologic Disease

An example treatment regimen using the methods, cells, and agents described herein for acute myeloid leukemia is provided below.

-   -   1) Identify a patient with AML that is a candidate for receiving         a hematopoietic cell transplant (HCT);     -   2) Identify a HCT donor with matched HLA haplotypes, using         standard methods and techniques;     -   3) Extract the bone marrow from the donor;     -   4) Genetically manipulate the donor bone marrow cells ex vivo.         Briefly, introduce a targeted modification (deletion,         substitution) of an epitope of the lineage-specific cell-surface         antigen n. In general, the epitope should generally be at least         3 amino acids (e.g., about 6-10 amino acids). Genetic         modification of this epitope of the targeted lineage-specific         cell-surface antigen on the donor bone marrow cells should not         substantially impact the function of the protein, and as a         consequence, should not substantially impact the function of the         bone marrow cells, including their ability to successfully         engraft in the patient and mediate graft-vs-tumor (GVT) effects;

Optional Steps 5-7:

In some embodiments, Steps 5-7 provided below may be performed (once or multiple times) in an exemplary treatment method as described herein:

-   -   5) Pre-condition the AML patient using standard techniques, such         as infusion of chemotherapy agents (e.g., etoposide,         cyclophosphamide) and/or irradiation;     -   6) Administer the engineered donor bone marrow to the AML         patient, allowing for successful engraftment;     -   7) Follow up with a cytotoxic agent, such as immune cells         expressing a chimeric receptor (e.g., CAR T cell) or         antibody-drug conjugate, wherein the epitope to which the         cytotoxic agent binds is the same epitope that was modified and         is no longer present on the donor engineered bone marrow graft.         The targeted therapy should thus specifically target the epitope         of the lineage-specific cell-surface antigen, without         simultaneously eliminating the bone marrow graft, in which the         epitope is not present;

Optional Steps 8-10:

In some embodiments, Steps 8-10 may be performed (once or multiple times) in an exemplary treatment method as described herein:

8) Administer a cytotoxic agent, such as immune cells expressing a chimeric receptor (e.g., CAR T cell) or antibody-drug conjugate that targets an epitope of a lineage-specific cell-surface antigen. This targeted therapy would be expected to eliminate both cancerous cells as well as the patient's non-cancerous cells;

9) Pre-condition the AML patient using standard techniques, such as infusion of chemotherapy agents;

10) Administer the engineered donor bone marrow to the AML patient, allowing for successful engraftment.

The steps 8-10 result in the elimination of the patient's cancerous and normal cells expressing the targeted protein, while replenishing the normal cell population with donor cells that are resistant to the targeted therapy.

Example 7: Effect of Gemtuzumab Ozogamycin on Engineered HSCs

As shown in FIG. 28, frozen CD34+ HSPCs derived from mobilized peripheral blood were thawed and cultured for 72 h before electroporation with ribonucleoprotein comprising Cas9 and an sgRNA. Samples were electroporated with the following conditions:

-   -   i.) Mock (Cas9 only),     -   ii. KO sgRNA (CD33 sgRNA-37), or     -   iii. Exon2deletion (dual gRNA 18+24).

Cells were allowed to recover for 72 hours and genomic DNA was collected and analyzed by PCR of the gRNA target region. To determine the percentage of cells having an exon 2 knockout were assessed by TIDE, and the percentage INDEL was determined. The fraction of the population with deletion of exon 2 was assayed by end-point PCR.

The percentage of CD33-positive cells were assessed by flow cytometry, confirming that editing with gRNA-37 was effective in knocking out CD33. FIG. 30. The editing events in the HSCs were found to result in a variety of indel sequences, as exemplified in FIG. 29.

(i) Sensitivity of Cells Having CD33exon2 Deletion to Gemtuzumab Ozogramicin (GO)

To determine in vitro toxicity, cells were incubated with GO in their culture media and the number of viable cells was quantified over time. As shown in FIGS. 31A and 31B, CD33 knockout cells generated with CD33 sgRNA-37 and CD33ex2 del cells generated with the CD33 gRNA-18 and gRNA-24 pair were more resistant to GO treatment than cells expressing full length CD33 (mock). 50% editing observed in CD33KO cells is considered sufficient protection in dividing cells. The initial decline in the viability of CD33ex2 del cells is thought to correspond to unedited cell death.

(ii) Enrichment of CD33-Modified Cells

To assay if CD33 modified cells were enriched following GO-treatment, CD34+ HSPCs were edited with 50% of standard Cas9/gRNA ratios. The bulk population of cells were analyzed prior to and after GO treatment. As shown in FIG. 31C, prior to GO treatment, 51% of gRNA-37 modified cells (KO) as assayed by TIDE and 15% of gRNA 19+24 (ex2deletion) as assayed by deletion PCR. Following GO-treatment, CD33 modified to cells were enriched at least 1.5× so that the percentage of KO cells increased to 80% and exon2delete to 50%. This data indicated that there was an enrichment of CD33 modified cells following GO-treatment.

(iii) In Vitro Differentiation of CD34+ HSPCs

Cell populations were assessed for myeloid differentiation prior to and after GO treatment at various days post differentiation. As shown in FIGS. 31D and 31E, CD33 knockout cells generated with CD33 sgRNA-37 and CD33ex2 del cells generated with the CD33 gRNA-18 and gRNA-24 pair showed increased expression of the differentiation marker, CD14, whereas cells expressing full length CD33 (mock) did not differentiate.

Example 8: Generation of Exon 2 or Exon 4 Deletion in CD19

NALM6 cell lines were transfected with indicated ms-sgRNAs to modify the CD19 locus as follows:

-   -   1) WT (wild-type, unmodified).     -   2) sgRNA 6+14 targeting introns 1 and 2 to generate the         CD19exon2deletion protein,     -   3) sgRNA 7+16 targeting introns 1 and 2 to generate the         CD19exon2deletion protein of CD19,     -   4) sgRNA 23+24 targeting introns 3 and 4 to generate the         CD19exon4deletion protein and     -   5) sgRNA 18 targeting exon 1 to create CD19 knock out.

Transfected cell lines were clonally selected and assayed for CD19 expression by fluorescence-activated cell sorting (FACS). NALM6 cells nucleofected with ribonucleoprotein of Cas9 and the sgRNA(s), as described herein, were maintained in cell culture for 48 hours.

Samples from the cell populations were assessed by Western blot using two different antibodies—one recognizing the Ig-like C2-type domain encoded by exon 4 and the second the C-terminus of CD19. Protein analysis of clonal NALM6 cells expression full-length or those modified with gRNA as indicated (NT=non-targeting control gRNA, WT=wild type). To confirm deletion of CD19 in gRNA nucleofected cells and modified CD19 in the CD19ex2deletion and CD19ex4deletion clones, lysates were blotted using a polyclonal anti-CD19 antibody (#3574 Rabbit anti-human CD19 Pab, Cell Signaling Technology) that recognizes the CD19 C-terminus. Western blot was performed on cells lysates with anti-CD19 antibody (OTI3B10, Origene) that recognizes the epitope encoded by exon 4 to confirm deletion of exon 4 in gRNA 23+24 nucleofected cells. Western blot with the C-terminus antibody confirms that CD19ex2delete and CD19ex4delete proteins are smaller than full length CD19. FIGS. 32A and 32B.

Example 9: Generation and Evaluation of Cells Edited for Two Cell Surface Antigens Results

Cell surface levels of CD33, CD123 and CLL1 (CLEC12A) were measured in unedited MOLM-13 cells and THP-1 cells (both human AML cell lines) by flow cytometry. MOLM-13 cells had high levels of CD33 and CD123, and moderate-to-low levels of CLL1. HL-60 cells had high levels of CD33 and CLL1, and low levels of CD123 (FIG. 33).

CD33 and CD123 were mutated in MOLM-13 cells using gRNAs and Cas9 as described herein, CD33 and CD123-modified cells were purified by flow cytometric sorting, and the cell surface levels of CD33 and CD123 were measured. CD33 and CD123 levels were high in wild-type MOLM-13 cells: editing of CD33 only resulted in low CD33 levels: editing of CD123 only resulted in low CD123 levels, and editing of both CD33 and CD123 resulted in low levels of both CD33 and CD123 (FIG. 34). The edited cells were then tested for resistance to CART effector cells using an in vitro cytotoxicity assay as described herein. All four cell types (wild-type, CD33^(−/−), CD123^(−/−), and CD33^(−/−)CD123^(−/−)) experienced low levels of specific killing in mock CAR control conditions (FIG. 35, leftmost set of bars). CD33 CAR cells effectively killed wild-type and CD123^(−/−) cells, while CD33^(−/−) and CD33^(−/−)CD123^(−/−) cells showed a statistically significant resistance to CD33 CAR (FIG. 35, second set of bars). CD123 CAR cells effectively killed wild-type and CD33^(−/−) cells, while CD123^(−/−) and CD33^(−/−)CD123^(−/−) cells showed a statistically significant resistance to CD123 CAR (FIG. 35, third set of bars). A pool of CD33 CAR and CD123 CAR cells effectively killed wild-type cells, CD33^(−/−) cells, and CD123^(−/−) cells, while CD33^(−/−)CD123^(−/−) cells showed a statistically significant resistance to the pool of CAR cells (FIG. 35, rightmost set of bars). This experiment demonstrates that knockout of two antigens (CD33 and CD123) protected the cells against CAR cells targeting both antigens. Furthermore, the population of edited cells contained a high enough proportion of cells that were edited at both alleles of both antigens, and had sufficiently low cell surface levels of cell surface antigens, that a statistically significant resistance to both types of CAR cells was achieved.

CD33 and CLL1 were mutated in HL-60 using gRNAs and Cas9 as described herein, CD33 and CLL1-modified cells were purified by flow cytometric sorting, and the cell surface levels of CD33 and CLL1 were measured. CD33 and CLL1 levels were high in wild-type HL-60 cells; editing of CD33 only resulted in low CD33 levels; editing of CLL1 only resulted in low CLL1 levels, and editing of both CD33 and CLL1 resulted in low levels of both CD33 and CLL1 (FIG. 36). The edited cells were then tested for resistance to CART effector cells using an in vitro cytotoxicity assay as described herein. All four cell types (wild-type, CD33^(−/−), CLL1^(−/−), and CD33^(−/−) CLL^(−/−)) experienced low levels of specific killing in mock CAR control conditions (FIG. 37, leftmost set of bars). CD33 CAR cells effectively killed wild-type and CLL 1^(−/−) cells, while CD33^(−/−) and CD33^(−/−) CLL1^(−/−) cells showed a statistically significant resistance to CD33 CAR (FIG. 37, second set of bars). CLL1 CAR cells effectively killed wild-type and CD33^(−/−) cells, while CLL1^(−/−) and CD33^(−/−) CLL1^(−/−) cells showed a statistically significant resistance to CLL1 CAR (FIG. 37, third set of bars). A pool of CD33 CAR and CLL1 CAR cells effectively killed wild-type cells, CD33^(−/−) cells, and CLL1^(−/−) cells, while CD33^(−/−) CLL1^(−/−) cells showed a statistically significant resistance to the pool of CAR cells (FIG. 37, rightmost set of bars). This experiment demonstrates that knockout of two antigens (CD33 and CLL 1) protected the cells against CAR cells targeting both antigens. Furthermore, the population of edited cells contained a high enough proportion of cells that were edited at both alleles of both antigens, and had sufficiently low cell surface levels of cell surface antigens, that a statistically significant resistance to both types of CAR cells was achieved.

The efficiency of gene editing in human CD34+ cells was quantified using TIDE analysis as described herein. At the endogenous CD33 locus, editing efficiency of between about 70-90% was observed when CD33 was targeted alone or in combination with CD123 or CLL1 (FIG. 38, left graph). At the endogenous CD123 locus, editing efficiency of between about 60% was observed when CD123 was targeted alone or in combination with CD33 or CLL1 (FIG. 38, center graph). At the endogenous CLL1 locus, editing efficiency of between about 40-70% was observed when CLL1 was targeted alone or in combination with CD33 or CD123 (FIG. 38, right graph). This experiment illustrates that human CD34+ cells can be edited at a high frequency at two cell surface antigen loci.

The differentiation potential of gene-edited human CD34+ cells as measured by colony formation assay as described herein. Cells edited for CD33, CD123, or CLL1, individually or in all pairwise combinations, produced BFU-E colonies, showing that the cells retain significant differentiation potential in this assay (FIG. 39A). The edited cells also produced CFU-G/M/GM colonies, showing that the cells retain differentiation potential in this assay that is statistically indistinguishable from the non-edited control (FIG. 39B). The edited cells also produced detectable CFU-GEMM colonies (FIG. 39C). Taken together, the differentiation assays indicate that human CD34+ cells edited at two loci retain the capacity to differentiate into variety of cell types.

Materials and Methods AML Cell Lines

Human AML cell line HL-60 was obtained from the American Type Culture Collection (ATCC). HL-60 cells were cultured in Iscove's Modified Dulbecco's Medium (IMDM, Gibco) supplemented with 20% heat-inactivated HyClone Fetal Bovine Serum (GE Healthcare). Human AML cell line MOLM-13 was obtained from AddexBio Technologies. MOLM-13 cells were cultured in RPMI-1640 media (ATCC) supplemented with 10% heat-inactivated HyClone Fetal Bovine Serum (GE Healthcare).

Guide RNa Design

All sgRNAs were designed by manual inspection for the SpCas9 PAM (5′-NGG-3′) with close proximity to the target region and prioritized according to predicted specificity by minimizing potential off-target sites in the human genome with an online search algorithm (Benchling, Doench et al 2016, Hsu et al 2013). All designed synthetic sgRNAs were purchased from Synthego with chemically modified nucleotides at the three terminal positions at both the 5′ and 3′ ends. Modified nucleotides contained 2′-O-methyl-3′-phosphorothioate (abbreviated as “ms”) and the ms-sgRNAs were HPLC-purified. Cas9 protein was purchased from Aldervon.

Target gRNA Target gene name Sequence PAM location CD33 CD33- CCCCAGGACTACTCACTCCT CGG CD33 gRNA37 exon 3 CD123 CD123- TTTCTTGAGCTGCAGCTGGG CGG CD123 gRNA19 exon 5 CD123- AGTTCCCACATCCTGGTGCG GGG CD123 gRNA25 exon 6 CLL1 CLL1- GGTGGCTATTGTTTGCAGTG TGG CLL1 gRNA4 exon 4

AML Cell Line Electroporation

Cas9 protein and ms-sgRNA (at a 1:1 weight ratio) were mixed and incubated at room temperature for 10 minutes prior to electroporation. MOLM-13 and HL-60 cells were electroporated with the Cas9 ribonucleoprotein complex (RNP) using the MaxCyte ATx Electroporator System with program THP-1 and Opt-3, respectively. Cells were incubated at 37° C. for 5-7 days until flow cytometric sorting.

Human CD34+ Cell Culture and Electroporation

Cryopreserved human CD34+ cells were purchased from Hemacare and thawed according to manufacturer's instructions. Human CD34+ cells were cultured for 2 days in GMP SCGM media (CellGenix) supplemented with human cytokines (Flt3. SCF, and TPO, all purchased from Peprotech). CD34+ cells were electroporated with the Cas9 RNP (Cas9 protein and ms-sgRNA at a 1:1 weight ratio) using Lonza 4D-Nucleofector and P3 Primary Cell Kit (Program CA-137). For electroporation with dual ms-sgRNAs, equal amount of each ms-sgRNA was added. Cells were cultured at 37° C. until analysis.

Genomic DNA4 Analysis

Genomic DNA was extracted from cells 2 days post electroporation using prepGEM DNA extraction kit (ZyGEM). Genomic region of interest was amplified by PCR. PCR amplicons were analyzed by Sanger sequencing (Genewiz) and allele modification frequency was calculated using TIDE (Tracking of Indels by Decomposition) software available on the World Wide Web at tide.deskgen.com.

In Vitro Colony-Forming Unit (CFU) Assay

Two days after electroporation, 500 CD34+ cells were plated in 1.1 mL of methylcellulose (MethoCult H4034 Optimum, Stem Cell Technologies) on 6 well plates in duplicates and cultured for two weeks. Colonies were then counted and scored using StemVision (Stem Cell Technologies).

Flow Cytometric Analysis and Sorting

Flurochrome-conjugated antibodies against human CD33 (P67.6), CD123 (9F5), and CLL1 (REA431) were purchased from Biolegend, BD Biosciences and Miltenyi Biotec, respectively. All antibodies were tested with their respective isotype controls. Cell surface staining was performed by incubating cells with specific antibodies for 30 min on ice in the presence of human TruStain FcX. For all stains, dead cells were excluded from analysis by DAPI (Biolegend) stain. All samples were acquired and analyzed with Attune N×T flow cytometer (ThermoFisher Scientific) and FlowJo software (TreeStar).

For flow cytometric sorting, cells were stained with flurochrome-conjugated antibodies followed by sorting with Moflow Astrios Cell Sorter (Beckman Coulter).

CAR Constructs and Lentiviral Production

Second-generation CARs were constructed to target CD33, CD123, and CLL-1, with the exception of the anti-CD33 CAR-T used in CD33/CLL-1 multiplex cytotoxicity experiment. Each CAR consisted of an extracellular scFv antigen-binding domain, using CD8α signal peptide, CD8α hinge and transmembrane regions, the 4-1BB costimulatory domain, and the CD34 signaling domain. The anti-CD33 scFv sequence was obtained from clone P67.6 (Mylotarg); the anti-CD123 scFv sequence from clone 32716: and the CLL-1 scFv sequence from clone 1075.7. The anti-CD33 and anti-CD123 CAR constructs uses a heavy-to-light orientation of the scFv, and the anti-CLL1 CAR construct uses a light-to-heavy orientation. The heavy and light chains were connected by (GGGS)3 linker. CAR cDNA sequences for each target were sub-cloned into the multiple cloning site of the pCDH-EF1α-MCS-T2A-GFP expression vector, and lentivirus was generated following the manufacturer's protocol (System Biosciences). Lentivirus can be generated by transient transfection of 293TN cells (System Biosciences) using Lipofectamine 3000 (ThermoFisher). The CAR construct was generated by cloning the light and heavy chain of anti-CD33 scFv (clone My96), to the CD8α hinge domain, the ICOS transmembrane domain, the ICOS signaling domain, the 4-1BB signaling domain and the CD34 signaling domain into the lentiviral plasmid pHIV-Zsgreen.

CAR Transduction and Expansion

Human primary T cells were isolated from Leuko Pak (Stem Cell Technologies) by magnetic bead separation using anti-CD4 and anti-CD8 microbeads according to the manufacturer's protocol (Stem Cell Technologies). Purified CD4+ and CD8+ T cells were mixed 1:1, and activated using anti-CD3/CD28 coupled Dynabeads (Thermo Fisher) at a 1:1 bead to cell ratio. T cell culture media used was CTS Optimizer T cell expansion media supplemented with immune cell serum replacement, L-Glutamine and GlutaMAX (all purchased from Thermo Fisher) and 100 IU/mL of IL-2 (Peprotech). T cell transduction was performed 24 hours post activation by spinoculation in the presence of polybrene (Sigma). CAR-T cells were cultured for 9 days prior to cryopreservation. Prior to all experiments, T cells were thawed and rested at 37° C. for 4-6 hours.

Flow Cytometry Based CAR-T Cytotoxicity Assay

The cytotoxicity of target cells was measured by comparing survival of target cells relative to the survival of negative control cells. For CD33/CD123 multiplex cytotoxicity assays, wildtype and CRISPR/Cas9 edited MOLM-13 cells were used as target cells, while wildtype and CRISPR/Cas9 edited HL60 cells were used as target cells for CD33/CLL-1 multiplex cytotoxicity assays. Wildtype Raji cell lines (ATCC) were used as negative control for both experiments. Target cells and negative control cells were stained with CellTrace Violet (CTV) and CFSE (Thermo Fisher), respectively, according to the manufacturer's instructions. After staining, target cells and negative control cells were mixed at 1:1.

Anti-CD33, CD123, or CLL1 CAR-T cells were used as effector T cells. Non-transduced T cells (mock CAR-T) were used as control. For the CARpool groups, appropriate CAR-T cells were mixed at 1:1. The effector T cells were co-cultured with the target cell/negative control cell mixture at a 1:1 effector to target ratio in duplicate. A group of target cell/negative control cell mixture alone without effector T cells was included as control. Cells were incubated at 37° C. for 24 hours before flow cytometric analysis. Propidium iodide (ThermoFisher) was used as a viability dye. For the calculation of specific cell lysis, the fraction of live target cell to live negative control cell (termed target fraction) was used. Specific cell lysis was calculated as ((target fraction without effector cells−target fraction with effector cells)/(target fraction without effectors))×100%.

Other Embodiments

All of the features disclosed in this specification may be combined in any combination. Each feature disclosed in this specification may be replaced by an alternative feature serving the same, equivalent, or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is only an example of a generic series of equivalent or similar features.

From the above description, one skilled in the art can easily ascertain the essential characteristics of the present invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. Thus, other embodiments are also within the claims.

EQUIVALENTS

While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.

All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.

All references, patents and patent applications disclosed herein are incorporated by reference with respect to the subject matter for which each is cited, which in some cases may encompass the entirety of the document.

The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one. B (and optionally including other elements); etc.

It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited. 

1. A population of genetically engineered hematopoietic cells, comprising: (i) a first group of genetically engineered hematopoietic cells, which have genetic editing in a first gene encoding a first lineage-specific cell-surface antigen, wherein the first group of genetically engineered hematopoietic cells (a) have reduced or eliminated expression of the first lineage-specific cell-surface antigen or (b) express a mutant of the first lineage-specific cell-surface antigen; and (ii) a second group of genetically engineered hematopoietic cells, which have genetic editing in a second gene encoding a second lineage-specific cell-surface antigen, wherein the second group of genetically engineered hematopoietic cells (a) have reduced or eliminated expression of the second lineage-specific cell-surface antigen or (b) express a mutant of the second lineage-specific cell-surface antigen, wherein the first group of genetically engineered hematopoietic cells overlaps with the second group of genetically engineered hematopoietic cells, and wherein the first and second lineage-specific cell surface antigens are selected from the group consisting of: (i) CD19 and CD33; (ii) CD33 and CD123; and (iii) CD33 and CLL-1.
 2. A population of genetically engineered hematopoietic cells, wherein one or more cells of the population: (i) have reduced or eliminated expression of a first lineage-specific cell-surface antigen relative to a wild-type counterpart cell, or express a mutant of the first lineage-specific cell-surface antigen, wherein the first lineage-specific cell-surface antigen is expressed in a primary cancer in a subject; and (ii) have reduced or eliminated expression of a second lineage-specific cell-surface antigen relative to a wild-type counterpart cell, or express a mutant of the second lineage-specific cell-surface antigen, wherein the second lineage-specific cell-surface antigen is expressed in a relapsed cancer in the subject.
 3. The population of genetically engineered hematopoietic cells of claim 2, wherein the first lineage-specific cell surface antigen is CD19 and the second lineage-specific cell surface antigen is CD33.
 4. A population of genetically engineered hematopoietic cells, wherein one or more cells of the population: (i) have reduced or eliminated expression of a first lineage-specific cell-surface antigen relative to a wild-type counterpart cell, or express a mutant of the first lineage-specific cell-surface antigen, wherein the first lineage-specific cell-surface antigen is expressed in a first sub-population of cancer cells in a subject; and (ii) have reduced or eliminated expression of a second lineage-specific cell-surface antigen relative to a wild-type counterpart cell, or express a mutant of the second lineage-specific cell-surface antigen, wherein the second lineage-specific cell-surface antigen is expressed in a second sub-population of cancer cells in the subject.
 5. The population of genetically engineered hematopoietic cells of claim 4, wherein the first lineage-specific cell-surface antigen is CD33 and the second lineage-specific cell-surface antigen is CD123 or CLL-1.
 6. The population of genetically engineered hematopoietic cells of claim 1, wherein at least 40% of copies of the gene encoding the first lineage-specific cell surface antigen has genetic editing and at least 40% of copies of the gene encoding the second lineage-specific cell-surface antigen have genetic editing.
 7. The population of genetically engineered hematopoietic cells of claim 1, wherein surface levels of the first lineage-specific cell-surface antigen in the population are less than 40% of surface levels of the first lineage-specific cell-surface antigen in wild-type counterpart cells.
 8. The population of genetically engineered hematopoietic cells of claim 1, wherein surface levels of the second lineage-specific cell-surface antigen in the population are less than 40% of surface levels of the second lineage-specific cell-surface antigen in wild-type counterpart cells.
 9. The population of genetically engineered hematopoietic cells of claim 1, wherein one or both of: the genetic editing of the gene encoding the first lineage-specific cell surface antigen comprises a frameshift mutation, and the genetic editing of the second gene comprises a frameshift mutation.
 10. The population of genetically engineered hematopoietic cells of claim 1, which are capable of growing in culture by at least 2-fold over 8 days.
 11. The population of genetically engineered hematopoietic cells of claim 1, wherein surface levels of the second lineage-specific cell-surface antigen in the population are less than 50%, 40%, 30%, 20%, 10%, 5%, 2%, or 1% of surface levels of the second lineage-specific cell-surface antigen in wild-type counterpart cells.
 12. The population of genetically engineered hematopoietic cells of claim 1, which are capable of engraftment.
 13. The population of genetically engineered hematopoietic cells of claim 1, wherein the hematopoietic cells are hematopoietic stem cells (HSCs).
 14. The population of genetically engineered hematopoietic cells of claim 1, wherein the CD33 pseudogene is not modified in one or more (e.g., at least 50%, 60%, 70%, 80%, 85%, 90%, 95%, 98%, 99%, or all) of the cells of the population.
 15. A method of supplying hematopoietic cells to a subject (e.g., a subject having a hematopoietic malignancy), comprising: (a) providing a population of genetically engineered hematopoietic cells of claim 1; and (b) administering the population of genetically engineered hematopoietic cells to the subject, thereby supplying the hematopoietic cells to the subject.
 16. A method of treating a hematopoietic malignancy, comprising: administering to a subject in need thereof the population of genetically engineered hematopoietic cells of claim 1; administering to the subject an effective amount of a first immunotherapeutic agent that targets the first lineage-specific cell-surface antigen, and administering to the subject an effective amount of a second immunotherapeutic agent that targets the second lineage-specific cell-surface antigen.
 17. The method of claim 16, wherein the first immunotherapeutic agent is administered when the subject has a primary cancer, and the second immunotherapeutic is administered when the subject has a relapsed cancer or cancer that is resistant to the first immunotherapeutic agent.
 18. The method of claim 16, wherein the subject has a cancer that comprises a first sub-population of cancer cells that express the first lineage-specific cell-surface antigen and a second sub-population of cancer cells that express the second lineage-specific cell-surface antigen.
 19. The method of claim 18, wherein the first lineage-specific cell-surface antigen is CD33 and the second lineage-specific cell-surface antigen is CD123 or CLL-1. 